If it was legal, it won't happen. Why? Because if they want to buy some weed, they have to go to a drug dealer who usually have other drugs to sell. It's the curiosity that lead them to harder drugs, not marijuana.
I'll call Bullsh*t. It's not as if you have to see a drug dealer to get alcohol or tobacco. On the other hand, going to see a drug dealer for ANYTHING speaks volumes of a person's character.