They were never a test to evade bots to begim with, most capchas were used to train machine learning algorithms to train the bots on ! Just because it was manual labour google got it done for free , using this bullshit captcha thingy ! We sort of trained bots to read obsucre texts , and kinda did the labour for corps for free !
I heard Captcha was being used as training data for self-driving cars. Which probably explains why almost all of them ask you to identify cars, motorcycles, bridges, traffic lights, crosswalks etc.
Not quite. When I used to care and kind of tried to distort the training data, I would always select one additional picture that did not contain the desired object, and my answer would usually be accepted. I.e. they were aware that the images weren't 100% lined up with the labels in their database, so they'd give some leeway to the users, letting them correct those potential mistakes and smooth out the data.
it won’t let me get past without clicking on the van
That's your assumption. Had you not clicked on the van, maybe it would've let you through anyway, it's not necessarily that strict. Or it would just give you a new captcha to solve. Either way, if your answer did not line up with what the system expected (your assumption being that they had already classified it as a bus) it would call attention to the image. So, they might send it over to a real human to check what it really is, or put it into some different combination with other vehicles to filter it out and reclassify.
I've found that a lot of sites use captchas or captcha-like systems as a means of frustrating users as a way of keeping away certain people that they don't want to access the site (intellectual property owners), though it's not the only tactic that they use. I mean it works, pretty much all of those sites are still up today, despite serving data that's copyrighted by Nintendo, Sony, and other parties.