Consuming alcohol is a cultural norm in many countries, including the US and the UK, and is heavily connected to sport. Its a social activity, it's a means to relax, or for some a part of who they believe themselves to be. In many sports alcohol is so deeply entrenched in the culture that its hard to imagine what it would look like without that post race/competition drink or drinks.
I grew up in show jumping, competing professionally as a young rider, up to about aged 24. Drinking in the evening at the event bar was as much part of the sport as the actual competition and for many, including myself, this was often far too excess. I even had a coach who believed it helped! His belief was that before a big competition, a few drinks the night before would mean that I rode more off instinct and would be less inclined to over think. There would have been many, many other ways to have achieved this result.
So what's the problem, is there one? Well, the research says yes, although as you might expect how problematic it is depends of how much alcohol is consumed, how regularly and when. So here are just a couple of observations in regards to alcohol and sport:
For up to three days after alcohol is consumed, it can decrease our reaction time and balance, as well as decreasing stamina and our ability to generate power.
Alcohol negatively impacts sleep by reducing time spent in deep sleep, a double hit when we that sleep for recovery. Even one alcoholic drink can interfere with your sleep quality, which often has a domino effect. Poor sleep for most means you're less productive, less likely to workout/eat right/effectively manage stress etc.
A number of studies indicate that alcohol decreases production of serotonin, melatonin (a important hormone for sleep), and testosterone and human growth hormone (both important for fitness/muscle gains).
Alcohol increases the stress hormone cortisol which also a key player in sleep/wakefulness and when elevated causes a range of problems throughout the body.
Recovery from exercise is slowed when alcohol is consumed. Alcohol consumption decreases our muscles ability to use glucose and amino acids. That means it negatively impacts the energy supply to muscles during exercise.
Here's the important take away - Its not an all or nothing! While some people may feel that alcohol simply brings no good to their lives, other may find it to be something they wouldn't want to live without. But just decreasing your alcohol consumption can make you a faster athlete.
References
Barnes, M. J., Mündel, T., & Stannard, S. R. (2010). Post-exercise alcohol ingestion exacerbates eccentric-exercise induced losses in performance.European journal of applied physiology,108(5), 1009–1014. https://doi.org/10.1007/s00421-009-1311-3
El-Sayed, M. S., Ali, N., & El-Sayed Ali, Z. (2005). Interaction between alcohol and exercise: physiological and haematological implications. Sports medicine (Auckland, N.Z.), 35(3), 257–269. https://doi.org/10.2165/00007256-200535030-00005
Hong-Brown, L. Q., Frost, R. A., & Lang, C. H. (2001). Alcohol impairs protein synthesis and degradation in cultured skeletal muscle cells.Alcoholism, clinical and experimental research,25(9), 1373–1382.
Shirreffs, S. M., & Maughan, R. J. (2006). The effect of alcohol on athletic performance.Current sports medicine reports,5(4), 192–196. https://doi.org/10.1097/01.csmr.0000306506.55858.e5