NFL Rules Forced Titans To Kick Extra Point In Yesterday's Game?

[Yavin4]

If you didn't see the Titans/Cardinals game (btw, thanks to the Favre lovers at Fox Sports for staying with a non-competitive game to the end), the Titans were down 4 and scored a TD with no time left on the clock. At that point, the game was over because the Titans had a 2 point lead with no time remaining. There was no reason to kick the extra point because there was no time left on the clock.

Yet, they did kick the extra point. Now, in OT, when a team scores a TD, there are no extra point attempts. The game simply ends. Is there an NFL rule that requires extra point attempts in regulation, even if they're irrelevant to the final outcome of the game?

BTW, the Cards were a 2.5 dog to the Titans. That extra point killed everyone taking the Cards and the points.