that's not even a social standard
I don't know what to tell you because it's kind of funny you think that to me. Next time you're at a restaurant look around at all the tables, try your best to estimate who is over 21 and who isn't. Count the number of people above 21 that are drinking some kind of soft drink (other than water), then count the number of people over 21 drinking some kind of alcoholic beverage.