I think Mimi has it pegged.

Also, if you don't exercise you get tired. If you're tired, you don't want to exercise! If you do exercise, you get more energy though unless someone has experienced it, they don't think that way. Not to mention that even though sometimes exercise isn't always fun (there have been times I've cursed quietly about wind, hills, or heat!) the feeling afterward could never be created artificially. It's all worth it at that time

Actually what gets me is this -- we have people at work who complain that they can't lose weight and yet they don't exercise!! Or else they exercise once and say it did nothing and therefore didn't work. Aaarrrgh!