And it also results in random decisions about who has their shoulders lower than their hips (or "hinging" as it is now known in some circles).
The problem is, if like Dan Palmer or Benn Robinson you pack extremely fucking low, and the other guy (e.g. Cheetahs' THP) is a big fat lazy bloke, then he's going to come down on top of your shoulders. If you can't hold him up, because the ref isn't down at your level, he'll make a judgement call about who had their shoulders too low, or reset the scrum. In those cases, you can easily lose because a lot of refs simply don't understand the mechanics involved, only that they've got a safety brief on this area of the game.
Which is why Phil Waugh should stop going for endless scrums. You're going to lose one eventually.