Going Smart and Low

In today's Bucs-Cards game, with under a minute left and the game in kneeldowns for the Bucs, Gruden's bunch was called for a 15-yard penalty for what I can only imagine was a post-whistle fracas. But it made me wonder...

If you're trying to kill the clock at the end of the game and avoid a punt, why wouldn't you take an intentional penalty on offense, so that you get the automatic clock runoff?

You'd have to commit the penalty before the clock was stopped, and a 15-yarder might be more yards than you want to give up... and I realize this is a rare situation, but still. In a situation where an offensive penalty helps you, there will be more than enough volunteers for the job (Jon Runyan, come on down!)...