Life is chaotic. It is impossible to control. For some, for those who want to control it and who feel out of control, they find control in drugs. They are the one thing in life that have a direct relation in life. You take a drug and feel good, bad, lazy or whatever effect you want. People who feel no control over life or emotions or themselves still have a need for control and when they cannot find it, they go to drugs to get it.
This is why those who don’t have a community, with ridiculous expectations, with a lot of stress or depression do it. Because they are those who need control but don’t have it and they often find it in drugs.