I'm around pools and spas a good bit and like having my phone near me to do stuff like control music and be able to respond to events without needing to get out of the water. Pools have killed quite a few of my devices in the past. Just the other day I tripped while working around the pool and fell in (quite dangerous, for sure) and I had my phone in my pocket. If it wasn't waterproof, I'd be out a few hundred bucks from that accident.

I also like to go hiking and camping a good bit. I've lost a few electronic devices from getting caught in a storm. Its nice having the peace of mind that it doesn't matter if I get completely soaked with my phone in my pocket.

Finally, I have kids, and they're of the stage where its fun to throw things in toilets and in sinks.