I literally just destroyed an iPhone which was in my pocket, in a case, and I apparently smashed it into a rock (which I wasn't even really aware of except it was rugged hiking generally). Probably protected my thigh.

I do carry a spare battery etc. I suppose I could keep my phone in a rugged case in my pack and use something else for pictures and maps but that's sort of getting away from the idea of one device you always have right with you.