Straight edge pretty much started with Minor Threat, who were too young to drink, as were most of their fans. The big black X on the hand was simply and old-school way of security marking the kids too young to drink. So, they started wearing it as a symbol of pride, e.g., NOT DRINKING and see my mark. It picked up other elements and other bands perpetuated it, all the way down through Earth Crisis (who I actually liked as a band, but their fans sucked) and Shai Hulud, and so forth. I mean, that shit was in conflict in Boston back when Siege and Repulsion were starting up, straight-edge versus regular punks who tended to do a lot of drugs, anti-metal, so forth.
Any actual significance in the movement is long since dead. Those who claim it are simply thugs with a somewhat atypical frame of reference, white kids who can't claim poverty or ghetto lifestyle for their anti-social behavior. Whatever claims exist against drinking or drugs, here's strong proof that those completely removed from use can be as absolutely as (if not more) useless to a society.