He drank heavily for decades - vodka and super-strength lager. As a kid, I don't think I ever once saw him without a can of beer at his side.
One day when I was 16 or so, he ended up in hospital because of his drinking. He decided he would stop drinking - and he just did, having only a single hiccup in the 10 years or so before he died. It was really quite incredible - that must have taken incredible strength and will power after decades of abuse.
I've had my own brushes with drink a long time back, and I fully agree with your reasoning - I think most people that use drink and drugs are able to do so safely and responsibly, and most of those that don't sink into habitual drink or drugs for a reason; trying to ease pain (physical or psychological), make life more bearable, or to escape it altogether.