The point of a run, especially on 1st down, is to get between 4-6 yards and open up the playbook for the next downs. If you are trying for a home run every play, you are instead going to get a lot of 2-3 yard runs and that basically is a wasted down and yes the RB will have some nice highlight film, but the runs that are not those will be killing drives. Barkley is great at getting home runs but terrible at consistently putting the offense in a position to succeed because he either gets 25 yards or 2.