Because in industry, it seems (in Germany) many Products, out of China too, use STM32, often ATmel, sometimes pic...
But in th US Communitys mostly Pics are used!!?
I use AtMega and ATXmega with Pacal from Mircroe, but there are other Pascal Compiler too.
FreePascal ist great, and works with STM32 and other ARM too..
C clearly, work for all.
The Flashing from Xmega is really easy, from Atmega realy good, ARM/STM32 really great..but Pic..I havent tryed it till yet, I bought some, but I can't flash it without special Programmer :-(
Ok, for Xmega you need an PDi Interface , its not so easy than Atmega
but this I have allready..so it was easy to convert to XMega..and STM32 btw ARM don't have so many cheap Discovery Boards