It's an incentive to show up. Employees tell management what they think, not what management wants to hear. Increase job satisfaction because if you have a bad job, you don't care. It makes fellow employees look better. It makes the cafeteria food taste better.
Bosses are more likely to hand out raises when they are wasted.
Eliminates the need for employees to get drunk on their lunch break. Increases the chance of seeing your boss naked.