Why 21?

I know we have all heard this debate about why the drinking age is 21 but yet a person can own guns, smoke, buy lottery tickets, travel alone, vote, buy porn, serve in the military, and so many other things at the age of 18. I was thinking about this today quite a lot. Today is my fiancees 21^st birthday today as well as a good friend of mines. I was also starting to notice a decline in the “quality” of celebration on a person 21^st birthday. This could be due to a wide variety of factors but then again it could be only one. People are drinking at a younger and younger age. In my high school there were freshman going to parties with upperclassmen and getting fallout drunk (so they say.). What is the attraction to underage drinking? Some say it gives you some sort of freedom that you otherwise never feel. Really? To me freedom is living on my own and being able to go out and have fun and not have to have a curfew among other things. People view this as differently as heads an tails on a coin which I find fascinating when I sit and listen to their reasons about how people aren’t as responsible at 18 as they are at 21. Well then think about this for a second shouldn’t all those other things I listed before be bumped up to 21?