a) you don't trust your kicker

and/or

b) you're pretty good at 4th down conversions.

In fairness, BYU has done well on 4th down conversions, but it is more tricky in the red zone, especially for passing plays. Also, that early in the game it's probably better to get 3 points than gamble. In the scenario presented, I'd probably kick, but I understand BYU trying to go for it given their track record. I don't distrust the kicker enough to not make a field goal that close (but didn't he miss a close one in the first game? now I'm second-guessing myself, but he has been solid otherwise, so now I'm second-guessing my second-guessing)