I have to agree with it being common in the law offices where I've worked (3 so far). They all have had at least some beer/champagne in the fridge.
My last job was very into drinking in the office - they had several kinds of alcohol, and one summer they even appointed one guy "bartender" and brought in a blender. We would have frozen drinks after lunch every Friday. They would also buy alcohol to drink at work after lunch on days when we were going out after work, like Christmas parties, etc (the career equivalent of pre-gaming?). We would have going away breakfasts with mimosas when someone was leaving the company. I'd never seen anything like it, and to be honest it made me a little uncomfortable sometimes - having frozen drinks while still sitting at your desk and trying to work is not necessarily my idea of a good time. All of my friends were jealous of my job though!