LOL, HN is really California-centric :) Ever heard of rain? I want to be able to use my phone in a rain, to call a taxi for example. Also, I don't want to worry about accidentally spilling a coffee on it.
FWIW, I live in Palm Springs, California, and in the early years lost phones not from jumping in pools, but from much of the year being 100+ degrees and even a couple minutes holding a phone to my ear and normal sweating would trigger the excessive moisture sensor and kill the device.