Obviously the lagalization of marijuana would have countless benefits (financial, medical and recreational), however, there's a very negative name attached to this plant: "a gateway drug". This means that a number of people (especially those who have little knowledge on the subject) may consider marijuana as dangerous as other (hard) drugs, and therefore be against legalizing it. Personally I think that both alcohol and cigarrettes, being potentially far more dangerous than marijuana, are the gateway drug.