Drugs were important for music. Without them, many things simply wouldn't exist. But this shouldn't be glorified; drugs have caused just as much suffering and misery.
In my first band - I was 15 years old -, rehearsals were basically parties. We drank an unbelievable amount of beer and smoked just as much weed. We often had girls over whom we'd met the night before at a club or a concert and thought we could impress. When I listen to the recordings today (we recorded practically everything), I can only laugh at our youthful stupidity. What we produced in a state of mental derangement was absolute garbage. Nevertheless, we managed to get good enough to play gigs regularly, which kept getting bigger. For a while, we were even relatively successful. Then two things happened that have shaped my opinion about sobriety in a band to this day.
1. We got so incredibly drunk before a big gig that it was a complete embarrassment. We kept messing up and had to restart songs. Between songs, I told stories that I thought were hilarious and clever at the time. They weren't. When I listened to the recording the next day, I was deeply ashamed.
2. One of the band members became increasingly addicted to cocaine and showed the usual symptoms. He told everyone that he was the "star" and we were just his backing band. When we found out, we fired him. That was the end of the band. Funny fact: He's a doctor now.
Since then, I've never drunk more than a small beer before a gig. Excessive alcohol or even drug use is out of the question for me in a band. Not only because you can't get anything done, but also because I don't want those kinds of people around me.