Because slippers are so much comfier and easier to take off when you want to lay down on the couch/go to bed and don't have to take shoes off to put other shoes on when going outside.
I don't have slippers, and my shoes are pretty comfy. If I want to lay on a bed, I'll take my shoes off, it's not hard. I use the same inside and outside shoes, cos I'm way to fking lazy to swap shoes when going in and out, if I had to then I wouldn't wear shoes inside. I'm not saying you should, so please don't reply with 40 paragraphs about why I shouldn't.
I just assumed you meant you had separate outside shoes and indoor shoes since you said "they aren't getting dirty" in your original comment.
If you're walking around your house with shoes you walk around outside in the yes, they are getting dirty. Even if you just use them to walk from your front door to your car and your car to your office.
I can't imagine walking around in my house in my shoes that I go to my office in, they get dirty enough without doing that.
Not saying you should change what you're used to, just saying that's definitely not the norm from where I live and can't imagine a situation where that wouldn't result in daily floor cleaning.
Over here there really isn't anything that would make shoes visibly dirty. The only time is when there's tonnes of rain and I take shoes off when that happens. Do you live in an area where it snows or is muddy? Those are the only reasons for needing to clean the floor often I can think of .
I live in Canada where it does snow in the winter so you have water/salt concerns but even in the summer there is still the risk of dusty dirt coating the bottom of your shoes and other random things, like bugs you step on, gum, gasoline at the gas station, a muddy puddle, etc.
I travel a lot for work and I even take my shoes off before walking around in my hotel room 😂 just a culture thing I guess.