It's no secret that QB's who can stay in the pocket and simply throw the ball away, are going to last a lot longer, and not lose efficacy nearly as much as running QB's.
If we compare Aaron Rodgers (38 years old, pocket passer) to Cam Newton (32 years old, running QB), the difference in their relative health shows who's going to have a longer (and better) career.
Rodgers looks as if he's still in his 20's, while Cam Newton is an old man at the age of 32 years old. Trying to run over those 250 lb linebackers on a regular basis isn't exactly a smart thing.