You don't see it at the NFL level because few owners want to see their multi-million dollar investment in harm's way (a lot of it guaranteed, when it comes to a QB...).
Folks have no problem with it in college because kids graduate anyway. Not to mention the good teams (OSU,... cough cough) have so many of them riding pine or waiting to sign that some are eventually forced to switch positions.
Cunningham failed at QB because Buddy didn't give two cents about offense and Jaws was a jerk to his understudy.
Wait a minute, my reply disappeared! You make a good point about Ryan, who called the spread offense "chuck and duck" and once got into a fistfight about it on the sidelines with Kevin Gilbride. And the Eagles' next coach was Rich Kotite who was terrible (Jets fans know that!). As for Jaworski, the idea of a "third-down" QB was bound to tick him off.
Your reply shows that it's not easy to use the mobile QB concept in the NFL. That's why I think Chip Kelly was mistaken in trying to transport it from college to the pros.