No matter how "bad" he is, you can't just be one dimensional. If they did that, they'd play a 3 man front all night and double cover the WR's.
For as bad as the run blocking is though, they could probably get away with it and still tackle him before he gets too many yards.
Running the ball and keeps the defenses honest and kills the clock (which is a good thing when you're winning). No matter how bad things are, there will still be run plays.