Straight edge came out of the hardcore punk scene, mostly associated with bands such as minor threat. Its no Drink and No Drugs, i think it was based around the idea that really you didnt need to do those things to have a good time at gigs, it then grew out into a subculture within punk.
Personally i can see where they are comming from that you dont need drink and drugs to have fun, but i think thats no reason for not enjoying those things.