Not once in my life I had thought "I would like to jump into this pool with my phone", while I did sometimes replace the battery on-the-go which actually made my life easier. It's an absurd take. If anything, I'd be more concerned with beverage spills, but these are still easier to avoid than drops.
Well you are the exception. Especially if you live in a hot area where a lot of people have backyard pools. Being in and out of the water constantly is a very normal in Florida for example.
Most the suburban kids in Houston had wristband attachments to their phones in the pool or would be in a floaty taking stupid pics of each other as kids do. Trying to keep a modern phone dry takes away a lot of utility.
Not a lot of people live in hot areas with plenty of backyard pools, but I can understand that waterproof phones could become more popular there than in the rest of the world based on this property alone (right now they're popular because there's not much choice).