Why would obama say the legalization of marijauna wouldnt help the economy?

In california alone they got like 3 billion in taxes just from medical users. If you know your facts it makes a lot of sense to make it legal to the general public. you can tax it. You make money, you no longer waste money in that department of the dea, and local police, you save money. You have a lot of high people doing less crimes. The test saying it causes brain damage was done on monkeys, they put a gas mask on them blowing nonstop for 5 minutes with no oxygen, 4 minutes of no oxygen causes brain damage. Since then they cant find any results saying it causes any brain damage. There are no known deaths caused by marijauna. More people die from drinking coffee then they do smoking weed. There are nothing but pros. The cons are only for high powered businesses. Cause hemp, the non smokeable part of the cannibis plant, can make clothing, stronger then cotton, bio fuel, cuts out oil use, wood, cuts out lumber. Wtf is wrong with our government?