21+ is only in the USA.

Ontario (province) has 19
Quebec (province) has 18

Most of the rest of Canada is 19, one or two more provinces are 18.
Most of the world is 18.

Just so you know...you don't have to drink alcohol. I drink one beer, then a lot of coke/pepsi.

You DON'T have to go to a bar for after-party. you can use the college/university campus cafeteria, a local restaurant or the college/university's pub.

If people don't like alcohol, DO NOT DRINK ALCOHOL.
I have no problem with a ginger ale.

Guess what? so many restaurants are licensed (they can legally serve alcohol), are we going to stop going to restaurants for after parties? So many events (not just WordCamp) go to dinner at a restaurant instead of bar.