Free Mediocrity

What is it about a day in meetings that makes me over-eat mediocre food? What is it about free meals that makes it seem important to get one's "money's worth". I spent today in a meeting center: I managed not to go nuts on the continental breakfast, but was intrigued by a brownie and ice cream dessert (so-so), cookies (barely edible) at the afternoon break and then had to have the full three courses at dinner.

What is it about free food that makes me eat stuff I wouldn't normally bother with?