I think governments should not meddle with what people choose to put in their bodies.. Simple. Do we have no freedom to do as we wish as conscious beings?
I also think there's a conglomerate of corporate powers constantly pushing for weed illegality because of several reasons, including how hemp would destroy the current rigged money-generating playing field. This would mean an excellent renewable source of everything hemp is good for, low cost, and abundant.
Max Igan here puts it wonderfully.