Sorry, but this reasoning that sealing a phone shut is first for water protection is bs. No mate, it's 100% first and foremost for planned obsolescence.
You know why? Go to your nearest store and pick up a 20-40 $ Casio watch that's 30m-200m water resistant, and check out the mighty innovations that make this happen while allowing you to operate its buttons under water and replace the battery and repair it: tiny rubber gaskets around the steel pushers and between the plastic body and the steel plate screwed down with 4 screws.
Surely the likes of Apple, who has more money than God, can copy this unfathomable innovation from the Casio F-91W, and engineer a similar gasket solution to unscrew the back panel on a phone and easily replace the battery while staying water resistant.
While unlikely to be true for readers of HN, for many people, their phone is the most expensive thing they own. So it has to be protected against accidents, and that's what the sealed design is for. Sure, it's probably good for planned obsolescence or whatever, but that's a secondary concern.
Another controversial aspect is that phones can't be repaired or sold for parts. This is another "loss protection" feature. Nobody steals mobile phones anymore because they are completely useless on the black market. The phone can't be used without the consent of the original owner, and the parts from that phone can't be put in other broken phones. The incentive to steal an easily-concealable $1200 brick of metal and semiconductors is nearly zero. I think that's amazing.