Earlier quoted context omitted.
Do you think they're screwing it in for fun? I'd rather my phone be more robust than worry about unscrewing a couple more screws when I need to replace the battery (hopefully a rare occurrence anyway). I don't know anyone that carried around spare batteries like in that ad, so although a good ad it doesn't really speak to customer usage. I'd also like my phone to be as-waterproof-as-possible, and am willing to sacrif…
They're doing it because they don't know better, or are deliberately ignorant to a generation of actually better designs. Waterproofing wasn't a feature people needed before the marketing told them they did.
Before my phones became waterproof, I lost multiple phones to liquid damage, so the idea that waterproofing is a marketing gimmick is nonsense.