I can make wine, to prevent me from making wine you’d have to make literally every fruit illegal, and even then there are millions of wild apple trees in my country that you’d have to cut down. It’s impossible to prevent people from making alcohol.
In contrast to that, you can’t grow anything that produces caffeine in my country. I’d have to import it, and checking mail in customs is a hell of a lot easier than checking the vast areas of empty forest to see if I’m illegally growing apples.