For instance would you give up a 15yd Penalty on tied game on Pit 10yd line with 4 mins left in game by having one of your defenders hit Rothlesberger on the head knowing he will get taken out of the rest of the game to be tested for concussion, when the hit would never keep him on the field before.
I think your example is flawed, because, if it were just a 15 yard penalty, then yes, go for it. Now, instead of just a 15 yard flag, you're getting fined thousands of dollars and then sitting out for a game or two. Would your absence from the upcoming games be worth taking him out?
Okay, well, to counter that, you could just put some 3rd stringer in and tell him to clobber the QB in the face. Well, if something like that happens, I can see the NFL fining and punishing entire organizations if something like that were to occur.