Being a ex.drug and alcoholic I was escaping the days of being beaten as a child. Myself and my sisters were all beaten by my mother with a electrical extension cord for years. The verbal abuse when we got older but its over. I forgave my mother she passed away I'm off off drugs and alcohol
Aside from the already answered, I'd say a lot of people find drugs to be an easy get-away from a tough life.
Otherwise, recreational drugs are better employed when trying to be.. Well, creative.
Mainly 2 reasons:
1 - Stupidity
2 - They got hooked on prescription drugs, and can't afford treatment.