I agree about adding waterproofing, but
The reason smartphones are fragile is because it is still a developing technology that has to keep getting better, faster. Unlike car electronics that absolutely have to be able to handle extreme temperatures and such, not being the best or fastest is the trde-off.
Anyone recall the G5 tower that had the first/fastest 2.5GHz top-end model that had to be liquid cooled because it ran so hot (2004)?