Take a look at it this way:
Jamaal Charles had 285 carries this season.
In 2011, LeSean had a similar season in which he carried the ball 273 times.
The difference in their running games outside of those 2?
The 2012 Chiefs also had Hillis and Draughan carry the ball 144 times for a whopping 3.75 YPC. The team ran the ball 500 times.
The 2011 Eagles next 2 leading rushers were Mike Vick and Ronnie Brown with 118 carries together and 5.5 yards per carry. They ran the ball 450 times.
Basically, the 50 extra carries the Chiefs had were ALL with backups and they were less productive to the tune of 2 whole yards per carry.
Efficiency is MUCH better than banging your head against the wall. The run doesn't keep the defense honest. Balance does.