Was payphones, i can think of plenty of reasons to have separate versions of each one.
Point and shoots still run circles around anything a cellphone can do. It's still a question of lens size/image sensor.
The big thing with these all-in-one phones, is that when your cellphone breaks or encounters a problem, everything breaks. That and when better components come out (mp3s, cameras) happen, you don't need to worry about upgrading everything or being left behind.