Yeah I have friends that have done that too. But like I say, if I had a choice between having to be careful with my device vs having to charge/pack an extra device on a continual basis it's a clear one for me ...
I suspect it is a clear one for a lot of people. The problem is that don't think it would be the same choice.
I moved back to Asia last year. And since then the combination of driving a scooter + rain season means my phone is soaked wet a couple times a year (sometimes it just rains and you really have no choice). If it is not waterproof, I have to always bring a backpack with me.