I met people asking why buying iPhone?
Not everyone want iPhone. iPhone is just not for everyone.
Different people buying iPhone for different reasons. Some people likes the big screen, some people like the touch screen, some people like the user interface, some people like iPhone application. Some people buy iPhone simple because it is an iPhone.
If you break it down one by one.
Easy to use interface? Why not Nokia?
Application? Why not Android, Palm or webOS?
Touch screen? How about HTC?
Big screen? Samsung Galaxy S with super AMOLED?
Now is the 4th generation of iPhone, if you still asking why buying an iPhone, then iPhone is just not for you.