Utah dares the refs to call pi on every play. They know the refs won't so they are taught to grab the receivers every play. They stack the box and grab the receivers every play. Players have to fight through it because refs are too cowardly to call pi every play when the pi is every play.
This does have 1 major flaw. If the RB breaks through the line they rarely have the safeties far enough back to stop a long run. See the ASU game. It is hard to do when everyone is in the box but when it happens then big runs are big.
Having reffed, I would love to be on the field for a Utah game. I would call 15 yard pi every play until they quit doing it. I wouldn't care if it was a flag on every play. It was easy to see schools who were taught to be loose with the rules like this when I reffed. A lot of refs would let them get away with it because of the mantra "let them play"