Feeling good is an evolved trait. We feel good when we have sex because it propagates genes. If we could hold technological growth static, the drugs that lead t

Feeling good is an evolved trait. We feel good when we have sex because it propagates genes. If we could hold technological growth static, the drugs that lead to dependence, depression, and suicide would eventually become less addictive. We do this with food through our tongue and through throwing up when we ingest poison. I'd imagine it'd be something similar for harmful drugs. Although it may be something else, like evolving out the negative consequences. Perhaps that's why alcohol dependence is correlated with intelligence: Smart people can think of ways of avoiding over drinking so there was less selective pressure on anti-alcohol dependence genes.