It encourages carpooling. It increases 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.
Salary negotiations are a lot more profitable.
Burping during a meeting is less embarrassing. Employees work later since there's no longer a need to relax at the bar. It makes everyone more open with their ideas. Everyone agrees the work is better after they've had a couple of drinks. It eliminates the need for employees to get drunk on their lunch break.