No, it's because Frazier is committed to the Nickel Defense, which is designed to stop the pass, not the run. Frazier thinks we are good enough to be able to stop the pass and the run with the Nickel.
GB demonstrated last week, our Nickel cannot stop the run. The Jets were watching and followed that game plan. Frazier is so stubborn, he won't change it up even though it's clear the other team is intent on running the ball down our throat.