People doing lots of drugs are probably trying to escape from something or otherwise self-medicate without realizing it (unless they're "psychonauts", and even then, they might still be running from something). I dunno about you, but eating candy makes me feel good (yanno, until it doesn't). Makes the pain go away.
Just something I've been thinking about after recently discovering the "trans people love weed" stereotype. As a trans person who loves weed, why? Well, it's less dangerous than heroin or alcohol but still numbs the existential pain of being trapped in a body that doesn't feel like it fits. I figure most people who consume drugs habitually probably do the same.
Alternatively, you might be due for a huge payday in the form of an anti-discrimination suit.