Waterproofing. It really is that simple. The math would never work out trading that for easy replaceability. And every average user can get a shop to replace their battery.
Waterproofing isn't a yes/no feature. Modern phones are way more waterproof and dust resistant than the S5. The plastic back on the S5 would quickly develop cracks that would let water in.
Sure, it wasn't perfect, but it showed that it can be done, and it's not particularly difficult either. An improved design could have a metal back panel instead of plastic, it could use screws instead of plastic snaps, etc. (And with most people using cases, who cares about visible screws?)
For the same reason I can't replace the battery on my electric car (not the 9V one). Because the car maker made that choice, for a myriad of good and bad reasons. What's your point?
I feel you. I just bought an exceptionally boring car in large part because it is meant to be largely user-serviceable. Sorry you got stuck with that problem.
My point was that GP made a strong assertion that didn’t quite bear up to scrutiny IMHO:
> I say this as someone who worked several years in engineering at Apple, and they were extremely environmentally conscientious years before it was a thing.
It seems to me that an “extremely environmentally conscientious” company would place a much higher priority on serviceability. But I am very open to contrary reasoning and I don’t know any Apple engineers. This was a rare opportunity.
I hasten to say that Apple products are so good I overlook this disadvantage, but then I don’t describe myself as extremely environmentally conscientious.