After the end of any banquets or receptions, any food that's left over is quickly packed up by cooks and/or stewards and taken home.
There's another co-worker who's afraid to invite anyone from work to her house because all of her silverware, glassware, dishes, coasters even ashtrays have all been taken from work.
If you ask people why they do it, you'll get a slew of different reasons. Some complain that they have no choice because of a freeze on salary increases and/or an additional 5% deduction in everyone's paycheck. Others say they see it as a chance at getting back at their bosses for mistreating them. And yet others steal for the simple thrill of it.