I can't speak for everyone, and I know that there exist many /. UIDs with a strong preference for dedicated devices... but for myself and the people I know, it's all about portability and flexibility.
There's an old saying in photography that the best camera to use is the one you have with you. The same thing goes for personal electronics. A few years ago, I used to carry around a backpack with the following in it:
- Spiral bound note pad
- Paperback book
- 10" laptop
- hand-held GPS unit
- cell phone
- portable CD player
- CD wallet case
- Canon Elph camera
- assorted and sundry other stuff
- extra batteries and charging cables for the above
- (I never got into portable game players, my bag was full--and HEAVY)
Today, I have two options. Either I just carry my iPhone in my pocket, or I include a small bag just big enough for my iPad and an external battery pack which can be used by either device. (if I bring the bag, I also tuck in a bottle of Ghost Pepper sauce--sealed up super tightly--because it's awesome.)
The crazy thing is, I haven't really lost much if any functionality over my previous carry, and at the very worst, it weighs less than 1/4 what it used to. I've also added a ton of functionality: always-on internet access is a big one. Also video recording and conferencing. (And 650k scoville hot sauce, but I digress.)
The absolute last thing I want at this point is to add yet one more device I would have to keep charged and haul around. I don't care if the games are 50 times better, 90% of the time that I play games I'm waiting in line somewhere and don't want a deep gaming experience anyway in the 2 minutes I have.