I think it's a generational thing. I used to mow the lawn for an elderly distant cousin, in the hot Florida summer weather. She would invite me in afterward for a snack and a 6.5oz Coca-Cola. I would guzzle mine in a couple of seconds. She would pour half of hers into a glass, over ice, and put the bottle back into the refrigerator.

Wine glasses have also gotten bigger over the years.