If that’s the case, how many times then will a team simply take a knee and not risk taking a PAT, if they could potentially give up 7 points?
The success rate for the PAT in 2013 was 1256/1261. Out of those 5 fails, 4 were blocked. A 0.32% rate to even have a chance to try to return the block for a td. Not getting that extra point can add up over the course of a game, and the average tds per game for a team was 2.38, so those non-attempts can add up to a field goal. Missing out on those points is not even close to being worth avoiding the 1/3 of one percent chance that the defense might block it, and the even smaller chance they’ll return it. Especially when the most common margin for a game win is only 3 points.
On another note, even though you can’t score off of a blocked PAT, you can still return it:
http://www.sbnation.com/lookit/2013/12/8/5189208/eagles-run-back-blocked-pat-dont-realize-that-it-doesnt-count