So a close friend really needed to lose weight for health reasons, but he kept putting it off. Too much life stress, etc. Anyways, one day him, his wife, and his daughter got together and made a bet; whoever lost the most weight in the next six months got $100 or some such.
Wife and daughter made some minor life mods and didn't worry about it too much. Guy took this as the impetus to go ahead and do a major overhaul and lost 30 pounds. Best thing that he could've done.
Short answer is: for some folks, it's irrelevant. For others, it's an excuse to try something new, get around to something that's been waiting, or get serious about something. But as this thread shows, it's one of those things that vary tremendously between people.