13-10. They missed a last second field goal

The rule was primarily intended to stop unethical coaches (imagine!) from sneaking in a player from the sidelines during the "trick" play. It also makes it easier to count the players, cause everyone's in front of the crew, and there's also some 'semblence' (sic) of order.
We see it. We call it. It doesn't happen twice. Five is better than fifteen.