plus all the $$$ spent on trying to stop pot growers each year would be nothing compared to the taxes they could make out of it, plus they need something to replace the ciggy taxes when they go.
we are not talking about harder drugs, just pot. and all the research claiming its a gateway drug are based in countries where it is illegal, none as far as I know have been conducted taking into account that the purchasing of it leads people into the shadier parts of society where hard drugs are more common and acceptable.