How bad a drug is should fall under the "would you suck a dick for it" criteria.
Schedules? Addictive potential? Potential for death? Nah throw that shit out the window, drugs should be classified under "would you suck a dick for it or not?"
Acid, mushrooms, DMT, 2CB? Nobody is sucking dick to get their hands on a tab of acid or an 8th of shrooms.
Weed? You hear a lot of stories about chicks sucking a dealers dick to get an 8th. It falls under the "would suck a dick for it" category.
Meth? Yeah, for sure people would.
Heroin or fent? Yeah, for sure.
Crack and coke? You betcha.
Ketamine and PCP? No, nobodies sucking dick for special K or Sherm.
Crack and Coke? Yes, a very strong suck a dick for it potential.
Alcohol. No, it can make you suck a dick, but nobodies sucking an alcohol dealers dick for a fifth of vodka.
Nicotine? Nope.
Ecstasy? Eh, borderline. Like alcohol, it can make you S a D, but I don't think anyone's S'in D to score a few Pikachus beforehand.
If you would suck a dick for a drug, it's illegal. If not, it's legal.