Whilst true to some extent, it isn't as new as we think. Window Mobile has been around for a very very long time and Palm OS preceded it with usable Palm Pilot devices.

Although it's not obvious, I guess popularity as a lot to do with ergonomics and usability and their evolution so something will only continue to be pushed forward if there's enough people to actually use it. I don't know, I'm just thinking out loud why something which has been on the market for such a long time only recently has seen such a crazy amount of innovation.