I think I understand that. One of the reasons is people try to act righteous. "Even though I'm killing myself I'll save you from ding the same coz I'm so righteous" They do the same thing even regarding alcohol or tobacco, they'll be drinking and say "You shouldn't drink it's bad for you, also tobacco causes cancer, don't start smoking *puff puff*". Also, weed isn't in a nice little package with a gold insignia.
I remember I bought a skullcap plant and my mum said is it dangerous? And I said not really but if you have to much it can cause liver damage. She basically went nuts at me saying why the fuck would I want to take something that can cause liver damage, while she had also been drinking that same day! To top it off, she bought me a packet of fucking skullcap a few months later from a health food store! lol coz she thought my plants were getting kinda low on leaves.
Truth is, nice packaging/marketing = safer and better in a majority of western society's eyes.