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.
If a cold beer and bonding time after a gym session make people more likely to exercise, I'd say it's a pretty fair trade-off.
It's just not that big of a deal unless you're training for something crazy
There are certain situations where I'd advise you to avoid alcohol after a workout. For instance, if you're a hardgainer trying to put on significant muscle mass for a bodybuilding competition, you probably don't want a beer or two to interfere with muscle protein synthesis. Likewise, if you’re a high-level athlete who needs to recover quickly between a series of back-to-back competitions (say, during basketball season), it’s probably not worth the buzz if a post-workout beer will delay your recovery time.