The offense could get a penalty and back them up or they could get sacked or stuffed. It happens all the time. You’re assuming it would be a gimme TD at the 1. So why didn’t the defender just tackle him to give the offense a harder shot at the TD??
OK, I will try this one more time. Which play are you talking about now? The situation I was talking about was the Brandon Cooks TD against MN, but you don't seem to want to talk about that play. If it is the long TD by Cupp, he was 5 steps ahead of Barr, so Barr couldn't have tackled him if he wanted to.
Yes, 1st and goal at the 1 instead of a TD is a Win for the Defense, but not as big of a win as a 15 yard penalty instead of a 50 yard TD would be, which goes directly to my argument. Do you not see the incentive for the Defense to commit PI under a larger set of scenarios if it was only a 15 yard penalty?