Also, removable batteries and waterproofing are not mutually exclusive. There have been flagships that were waterproof and had a removable battery, like the Galaxy S5. And there still are phones like that. Manufacturers have taken this away from us.

Also, also, every other industry has seemed to have figured it out. Go to the dollar store and you will find a flashlight that is waterproof and has easily replaceable AA batteries. Its not that complicated. Apple is one of the most successful companies on the planet, they can hire an engineer to come up with a decent solution. Apple et al. using waterproofing as an excuse to make the entire phone disposable when, not if, the battery dies is bullshit.

Idk waterproofing/resistance is a nice feature to have, even if it's just for the peace of mind. There are more instances where your phone might get wet. Heavy rain, spilling something on it (maybe even in a bag where it'll be exposed to it for longer). Accidentally falling or getting pushed into water.

But I guess mostly the peace of mind aspect e.g. when using it near water. Water damage is an unplanned accident, battery degradation is slow and doesn't have the same risk of suddenly leaving you without a phone (that serves many purposes nowadays). So that is a different kind of risk people want to have some insurance against.

However as someone else said repairability and a decent IP rating don't have to be mutually exclusive.

Lots of people I know use their iPhones to take pics in wet environments, and push the water proofing to the limit.