Your argument is further discredited by the fact that you have not even told us WHY they should be 21+. Other than the fact that you are quite possibly a huge asshole, or just have something against teenagers having the opportunity to live a good life, for some reason.
The DC music scene has always thrived upon the all-ages aesthetic. Ian Mackaye was 17 YEARS OLD when the Teen Idles began. 18 with Minor Threat. Part of the culture and appeal of this music scene is the fact that it is accessible to kids of all-ages, and it always has been. I'm really sorry if you don't like kids, but regardless, most of what we have today wouldn't even be here if it wasn't for those teenagers attending and playing the shows that they played in the late 70s.
I don't know why you see something wrong with giving kids an outlet. They aren't stopping you from drinking or having a good time at shows. If they are, you are far too easily irritable.
As far as I'm concerned, if someone gets something really valuable out of what we have, and it's safe, why the hell deny that of them?
I had a lot of friends into some pretty hard drugs at a young age and I never touched a drug in my life because I spent my time away from them with my new straightedge friends in DC (...this, by the way, had nothing to do with saving my life). I avoid a lot of stupid drunk high school parties now because I'd rather spend my time sober, seeing a nice band, with other sober people who are into the same music as me. I do better in school when I'm happy and involved in something that I like. I'll probably get admitted to college because of my concert photography. And there isn't anything wrong with that. There shouldn't be anything wrong with that.
And by the way, a kid at my school was almost killed three weeks ago when he was hit by a schoolbus crossing right out front of our school to go home. Real fucking safe.
Nebraska, also, has a quite nice indie music scene...