Hey Tinpis, because its a good time to relax away from work!!!
And if you drive or fly after alcohol, well you deserve what you get. The term "responsible" comes to mind. I remember 30 years ago was my last trip and was very enjoyable to get out and enjoy time with friends, doing what we love (flying).
Some of the best learning for new pilots has always been done around a bar. My generation was like that, And I'm sure more recent generations too.
maybe someone should put together a list!