A comment from @JRCX in a related thread pointed up a weakness in the historical thinking behind the standard drink. This illustration (again from the wikipedia article) summarizes the cute reductive thinking at work:
So, as long as your drinking is limited to what you see 1 == 1 == 1 == 1. Count ’em up. Of course, that’s just not how a lot of us drink, today.
Hell, a couple craft beers from the ubiquitous tall boys could easily be 3 standard drinks.