The most off-putting thing about "hard drugs" for me is the addiction factor.

With weed at least, I can smoke a bowl a day or two, and not want to smoke again for months. It's just a passing whim, like having a glass of pineapple juice.
But I know that if I started shooting heroine, I would get addicted in a matter of days, not to mention I have an addictive personality. So it's not really alluring when I hear how dependent they make you.