It's bizarre to me that we've gotten so used to disposable things these days that we're conditioned to think of replaceable batteries as an odd feature.

I remember when Powerbooks had batteries that were not just user-replaceable, but field-replaceable.

Important thing to note with AirPods is that it’s not just the batteries that deteriorate. All of the membranes and meshes and everything lives in a constant chaos of heat/cold, grease, shocks from being dropped, etc. If you get a new pair of AirPods Pro after two years they sound significantly better than the old pair. I’m on my third pair and I never once bought a new one because of battery life/failure.

I largely agree with you. I used to work at Cochlear (hearing aid implants) - their "headphone" equivalents actually had neatly replaceable batteries 10 years ago, it's doable! Larger than airpods, to be sure, however i'm sure Apple could shrink them nicely. But... would anyone want the ability to replace batteries? I wouldn't know. I suspect most people misplace them before the batteries go bad.