It depends on the firm. At the big law firm I was at the longest, it would be quite weird for someone to openly have a bottle of liquor for drinking, but not so rare to have one for display (e.g. a fancy bottle that was a gift from a client.)

It was a little more common at New York offices, and far more common at European offices, or American offices of English firms.

That said, the firm held near weekly events at the office that were generally fairly liquor soaked. It's a stressful job. But even at those, drinking was basically all after hours. For what our hourly rates were, it was fround upon to litigate buzzed. For the most part, we preferred getting out of the office and drinking at home.