Other niche features like water resistance can be achieved other ways, like suitable cases or removable sealing compounds along seams. Engineers are clever, they solve problems the simplest way possible within a given set of constraints. Changing those constraints won't change the possibility of achieving similar outcomes.
> If more people wanted them, more people would sell them, but most people prefer the additional battery life, increased water resistance, and thinness of modern phones.
You're overstating the preferences and availability of alternatives here. All the best engineering talent went towards sexiness hype cycles, little went into making phones with that were more eco friendly.
Lots of people also liked Tho-Radia, a radioactive cosmetic from almost 100 years ago. That's not a justification for permitting it.
> Other niche features like water resistance
For myself, and nearly everyone I know, water resistance is a must have and battery replacement is the "niche feature". I've lost WAY more phones due to water related accidents than I have to bad batteries.
If phones were more repairable, then water wouldn't destroy the whole phone and you'd maybe just have to buy a new battery.
If you mandate everything has to have replaceable batteries, you restrict the ability for consumers to choose devices that prioritize other things.
Only logic that I would say could be used is an environmental concern, but you'd need to really show that replaceable batteries would lead to significant improvements in the amount of e-waste we generate. If everything has a replaceable battery, but only a few people take advantage of it and the average lifetime of a phone remains constant-ish, it's really not valuable.
I think the replaceable battery thing is very much a HN bubble issue. It's not like there aren't phones with them. If more people wanted them, more people would sell them, but most people prefer the additional battery life, increased water resistance, and thinness of modern phones.