Well, there's some common sense involved. Your defense has problems so you don't want to expose them and play from behind. If a team has a top defense, I could see it.
Practice squad defense is actually going into the playoffs worse than last year. It's too bad, fans had high hopes. But no matter what, it's been a fun and historic season.
Play from behind for a slight chance to get the ball just before halftime. If my team had a dominat defense, I may defer. With 8 starters on IR? Take the ball....