Is there an evolutionary advantage associated with armpit sweating and stinking?

Just as a reminder, it's also good to ask "is there any big disadvantage?". Sometimes, a thing evolves traits that don't help but don't cause enough harm to stop being passed on.
- It's interesting how many people don't realize this. We were having a casual discussion one day and one of the smartest people I know, who has been educated in a lot of science, didn't realize that neutral or even outright negative traits can occur and persist in evolution. Evolution doesn't create a perfect being. It's just creates those that can survive long enough to reproduce better than those that can't do it as well.
  
  “There's no such thing as survival of the fittest. Survival of the most adequate, maybe. It doesn't matter whether a solution's optimal. All that matters is whether it beats the alternative.”
  ― Peter Watts, Blindsight
  Another good one:
  “Evolution has no foresight. Complex machinery develops its own agendas. Brains — cheat. Feedback loops evolve to promote stable heartbeats and then stumble upon the temptation of rhythm and music. The rush evoked by fractal imagery, the algorithms used for habitat selection, metastasize into art. Thrills that once had to be earned in increments of fitness can now be had from pointless introspection. Aesthetics rise unbidden from a trillion dopamine receptors, and the system moves beyond modeling the organism. It begins to model the very process of modeling. It consumes evermore computational resources, bogs itself down with endless recursion and irrelevant simulations. Like the parasitic DNA that accretes in every natural genome, it persists and proliferates and produces nothing but itself. Metaprocesses bloom like cancer, and awaken, and call themselves I.”
  ― Peter Watts, Blindsight
  
  ...evolved down the wrong path, almost as if its devolution
- Yes, it makes sense

Between 80 and 95% of East Asians have a dysfunction of the ABCCII gene, which is linked to smelly pits, a number of studies say. And this means their bodies don't release the same acidic odor smell the rest of the population does when exposed to hot temperatures and perspiration.
Also causes dry earwax

Something I haven't seen mentioned here is the fact that sweat acts as a lubricant between the skin of your torso and upper-inner arm preventing chapping with increased skin-on-skin contact movement.

Yes, the sweat keeps you cool and the smell attracts others with different immune system.
- My partner’s sweat smells so fucking UNFFFFF and has for the last decade and I cannot get enough of it aaaaaaaaaaaaaaaa
  
  You're a girl I imagine? I feel like girls are more likely to experience this than dudes. Anecdotal of course
- Can you develop the part where the smell attracts people?
  
  https://en.m.wikipedia.org/wiki/Claus_Wedekind
  
  One (old) piece of advice I heard.
  Your pocket handkerchief. Rub it on your balls. Then put it back in your breast pocket.
  You will get more attention from the girls.
  Pheromones are real and powerful.
  
  I think all humans have some kind of natural scent that can be used to "find a mate". Not everyone will find that scent attractive but your potential partner might. It's basically a way we evolved to find a partner to reproduce and get stronger as specie. Of course someone who better understand can correct me.
  
  Get a load of this loser who doesn't know about girlsmell lmao 😏

Sweating allows us to run prey to death.
- Found Singed main

Hormones are weird. We can smell things we don't think we can smell.
- You meant pheromones.
  
  I meant human stink particles
- When she's turned on. I can smell it. But it isn't really a smell. Like I'm unconsciously smelling it and then my unconsciousness taps my consciousness on the shoulder.
- Did you mean pheromones? There is no evidence that humans are affected by pheromones.
  
  https://www.pbs.org/wgbh/evolution/library/01/6/l_016_08.html

Sweating is good for heat management, the smell is useful for mate selection.

Supposedly the smell was something prehistoric people would flaunt. Mating in a lot of species is odor-based, and at one time, we were no exception. They did an experiment in an episode of a science program called Brink where they made a pheromone system that could be used to detect how related you were to a potential mate and found it successful. For us, they say, it just happens to gather in our armpits.
Whatever prehistoric people thought, nowadays we seem to dislike body odor and tend to favor filling the room with a mist of Old Spice.

My understanding is that our armpits wouldn't stink (as much) if we did the same thing as our ancestors - that is, not wash them with soap and use deodorants. I think there are supposed to be naturally occurring bacteria that will keep the stinky bacteria in check if we didn't kill them with that stuff. I haven't read anything in depth about this though.
As for sweating under the armpits, sweating in general helps us cool down our temperature. I wouldn't be surprised if armpit sweat also helps lubricate an area that would otherwise be prone to chafing when you're active.
- I mean, here's another thought...
  A lot of animals in the wild stink. Seriously. Check out a farm or a zoo. It's quite possible that people just used to generally smell bad before the modern age.
  But I guess a positive to this is, you know how you get used to a smell if you're around it all the time? Like say you eat McDonald's in your car on a long car journey. Nothing is out of the ordinary smell wise to you. But then you get to your destination and leave your car for a few days. You come back and notice it smells like shitty old McDonald's because you had been away from it for a bit. What I'm getting at is if we were around stinky people all day we maybe weren't bothered by it as much because you can go "nose blind" to that sort of thing after being exposed to it often.
  
  A lot of animals in the wild stink. Seriously. Check out a farm or a zoo. It’s quite possible that people just used to generally smell bad before the modern age.
  That's definitely something to consider, but when I really think about it I'm not sure I completely agree with this. I am sure that some animals smell more than others, but also that a lot of the smell you notice especially in zoos is because you're smelling their poop nearby. I think if you take most animals away from their bathroom area you may notice much less odor on their bodies.
  I think of cats as an example, since I'm most familiar with having them at home. Cats are typically nearly odorless unless they have some health issue. They may not be the best example though, since they do clean themselves all the time unlike most other animals. Another thing to consider is how would those animals smell if they ate their natural diet that they would eat in the wild. I think that would also have an effect on their smell.
  In short, I don't think there's much evidence that humans stunk to high heaven before the invention of soap and deodorant. I would gladly consider the evidence though.
- I encourage you to stop washing your armpits and not use deodorant. I’m sure the people around you will appreciate your decision and the special bacteria involved.
- I do use soap but not anti bacterial soap, just dr bronners. But I really scratch with my finger nails. Anyway I don’t wear deodorant. I don’t smell until 2-3 days without a shower.
  
  Lucky!

We don't have the organ to sense pheromones, but we weren't going to lose the ability to produce them first.
But also, it's an armpit. A big slab of meat touching one of the hottest parts of your body. It's going to trap heat which stimulates sweating.

About the stinking, you would better look for these bacteries advantage :)

Yes, because it gets hot between your arm and the side of your torso, and the stink in the buildup of normal bodily bacteria is larger concentrations. Fun fact the bacteria in your armpit is the same bacteria that is resistant to Methicillin (MRSA, Staphylococcus aureus.)