I say you do it. It's pretty much the same reason Mike Tomlin did the onside kick. Both teams had lots of evidence that either of them could score on the other at their own will. A shootout like that usually ends with whoever has the last possession.
People saying "well we could fumble the snap." I doubt there has even been a fumbled snap on a kneel down, EVER. If any team ever loses a fumble on a kneel down they deserve to lose no matter how many points they're winning by.
People are also saying "Crosby might miss it, he shanked two extra pointers earlier." If you saw the extra points Kapinos shit on both of the holds, it was terrible. Plus what better way to instill a little bit of confidence in a shaky kicker than giving him a game-winning opportunity?
Strategically speaking, you kneel it, run the clock and kick the field goal. However, I believe that in the moment nobody is really thinking about it and you take a touchdown when you can get it.
Our defense should have held on that final drive. There were so many "if" scenarios where we should have closed out the game. If Chillar hadn't chipped on the play he got the pick; if Josh Bell had pushed Mike Wallace out; if the Steelers didn't convert on one fourth down and three third downs; if Cullen Jenkins could have wrapped up Roethlisberger on the second to last play; if Charles Woodson hadn't been called for a holding penalty; if Capers had applied more pressure to Roethlisberger. Play this final drive out again a hundred times and the Steelers don't win it. Nothing went in our defenses favor and it was a truly tough loss for us and remarkable win for the Steelers.