It's good for bonding and motivation
There's no question that alcohol is a social lubricant -- it loosens people up a little, gets the conversation flowing, and helps turn a standard workout into an event… or an event into a party.
Just take a look at all the races that now offer beer to participants at the finish line (Tough Mudder and Spartan Race are just two of 'em). Race directors know that finishing a tough event is celebratory, and that participants want to hang around with other racers to talk about the experience. Offering beer at the finish line is a way to encourage people to stick around, to cheers one another, and amplify the celebration. And if people end up having a good time, they’re more likely to sign up for more races.
The concept doesn't just apply to races themselves, though. Casey Wetjen, a dedicated runner, points out, "My husband and our group of [running buddies] felt that a beer after a training run was a must." She joked the decision was based on the need to carb load, but really, it was more about turning the pain of a tough workout into an enjoyable social event. It offered a reward at the end of a grueling experience.