The following is just one opinion, with several aspects to the opinion. I, for one, like the rule as written. Pass interference tends to be one of the most controversial penalties in football. Perhaps half of those calls are clear; but the other half seem to be very questionable calls by the officials. Why give the offense a 40-yard advantage by making a questionable call on a long pass? I would rather the offense have to earn the yardage rather than officials gifting them the yardage. Secondly, in most cases a 15-yard penalty will give the offense a first down. That in itself is a worthwhile advantage for the offense. And lastly, (although I may be wrong on this), I do not think a game can end on a defensive penalty. Consequently, at least on a technical level, the scenario you describe above cannot happen. The defense would not be able to end a game with repeated penalties. If the defense commits a penalty as time runs out on the game, the offense would be given another play as an untimed down.
