"Would you like to buy a candy bar for my daughter's school fundraiser?" "No thanks. I'm not hungry." "That's not really the point." "Why would I buy an overpriced candy bar if I didn't plan on eating it right away?" "You'd do it because your coworker asked you to." "That's a reason?" "Yes, it is." "In that case, I'll take one." Five minutes later "Hey, coworker, would you like to buy a half-eaten candy bar?"