[jpace121]

There is something to be said for having the underlying hardware be relatively simple. Someone who started with Arduino could reasonable be expected to grow, study the data sheets, and progress on to AVR C. Moving from the Arduino API to any of the other things supported by ARM is quite a jump to make in a single leap, without some sort of intermediate learning step.

[drewm1980]

Exactly. I would add that the same is true of the hardware. You can easily pop the DIP chip out of a classic arduino and build your own circuit around it on a breadboard. Making your own surface mount board is a much bigger leap.