The only good reason I have ever heard, not to consume illegal drugs, is precisely that. You don't know what you are being given. Illegality destroys quality control, by making you unable to look for redress through the legal channels for fraud. You had a paper bathed in nothing. Others have blow cut with baby powder. Others have pot mixed with whatever plants grow in the area. Others have heroine baked with chalk. Others have meth with residues of corrosive acids.

Stick to tobacco, alcohol and glue. You do know what there is in those.