The bit about acting as social glue makes some sense to me, although to be honest it still seems somewhat problematic. Even discounting people who don't drink for whatever reason(alcohol dependance, religious views, health, etc) I would think that alcohol would pose just as many potential problems as it would aim to fix.
I'm obviously bringing a huge amount of personal bias to this discussion, but I'm probably exactly the kind of person who might benefit from the social aspects of drinking. I'm normally very shy and reserved, a beer or two often helps me relax and enjoy the company of others without my normal anxiety. Of course, a few too many beers results in me being too talkative and boisterous. In a social situation amongst friends, this would be no problem, someone would just tell me to calm the fuck down, I'd be momentarily embarrassed, and no one would think anything of it. At work however, it may pose more longer lasting problems with how others view me, or how I think others view me.
Again, I'm not judging anyone else who enjoys this kind of workplace, and I understand that what holds true for me may not be true of others, I just wanted to give my two cents.
However, there are other cultures where it's a huge smell for, umm, fratty culture. Don't ignore your gut on this unless you like cleaning up your boss's puke and feeling a stigma for staying dry. I've also experienced this and it was really fun for a small startup where everyone is friends—it needs to be carefully managed as you grow; you lose employees this way.
These policies also make so much more sense with small offices where everyone knows each other.
Finally, there are typically stringent "on call" policies for people in control of deployed infrastructure to ensure they don't drink. People further away from the money don't need this as much.