You're right. That's just disgusting. I'd definitely say that as soon as you get the idea that you "might" get the urge to go, that you probably need to head to the bathroom right then if your dress takes a long time to get in and out of (or you can't just lift up all the skirts to go potty). Thankfully I'll be wearing pants to my own wedding and I don't think I'll have to worry about this issue. My future bride, however, might. I'm pretty darn sure that she won't be wearing any diapers either.
my sis was wearing one. not sure if she had to use it, lol