We have our own phone, it's the iPhone. I paid the money for it because I wanted the full package. You can buy your own kind of phone that's not the full package. Many different vendors are making that.
So no, the average smartphone buyer does not swim with their phone. Manufacturers had other incentives to make changing the batteries harder and there was no pressure from customers to increase the IP rating. In fact all you hear is people ranting how much it sucks that batteries are so hard to change these days.