because they realize that to be the big dog in your own market, you have to win that game or you are just a joke to the local fans.

utah is so new to big time football that they really don't know how to behave.

by canceling the game and not playing it, here's the situation they put themselves in. they have a few losing seasons and then the fan base jumps on them for basically being oregon state, washington state, arizona and other bottom feeder PAC programs and they no-longer have the ability to point out how they beat BYU head to head and "save their season" with one win. so the perception only gets worse for them.

they've done the math and have come to the conclusion that playing the game and losing is worse PR for them than just not playing the game and hoping nobody notices how weak they really are.