My maybe unpopular thought: There are legal/illegal (relatively)healthy/unhealthy drugs/foods. We already have many legal/healthy, many legal/unhealthy, very few illegal/healthy, and many illegal/unhealthy drugs/foods. It seems that hemp is considered to categorized to illegal/(relatively)healthy drug (only for adults?). So I can think that keep it on the category is somewhat good for who want to do bad thing. Of course it depends on the situation in each country.

Disclaimer: I have no experience.