Because it is, statistically, an easier and more pleasant experience. I really get tired of taking twenty minutes to configure a bunch of settings for each marginally novel piece of tech I acquire.

Maybe they don't mind putting the adapter on their headphone cable? If you aren't switching devices a lot, it's a one-time operation that's pretty easy to manage.

Because I don't miss anything about old phones. Yes sometimes the airpods can work a little funny, but on a whole, they are so far ahead of the wired headphones I used to use that I can completely forgive the issues they have. Yeah it was cool to put an SD card in my phone, but it never worked that seamless and my phone now has more storage than I'll ever use.

I think of it like USB A ports. You miss it for a few years. And then you don't. And the products generally continue to improve along other lines