Cross culturally, sober may also have different definitions.

In my part of the world, an awful lot of people drink a heck of a lot. Enough to be considered alarming in America. But, we're not dependent on alcohol (it's for business/ pleasure) so not fulfilling the criteria of 'functioning alcoholics' either. Although there are a lot of these too.

Tonight I've had six pints of beer and two shots, and that's a light night. When I'm working full time and the champagne and wine are flowing generously and I'm expected to socialize two or three nights a week, it can be a lot more - and I don't really even get drunk.

My point is, it might be less openly acceptable in the United States, but your therapist (or anyone) could easily be concealing a heavy drink habit and clients would be none the wiser. You never know.