With all due respect, I wish people would keep judgment out of a thread meant to express loss and grief and pay tribute to someone.
When it comes to drug abuse and/or addiction, you can't understand it without understanding personal pain, and without a healthy dose of empathy and compassion. For far too many, drug abuse and/or addiction are a form of self-medication. Get that through your judgmental heads, and it starts to make a kind of sad sense.
Otherwise, keep your judgments to yourself. You might want to look for your compassion too. You've probably got some somewhere.