The make outcome helps you more than the miss outcome hurts you.
You still have to score a TD and a FG in either scenario.
In the scenario that you just kick the PAT, and then kick another, then you have to win overtime.
In the scenario that you kick the PAT, then go for two at the end of the game to win it, you're limiting yourself to one chance to win or lose.
If you go for 2 on the first one, you give yourself that chance to (be set up to) win, but you still have another chance to tie if you don't get it.