Why is marijunana not legalized? (For the haters out there)?

did you know marijuana is already decriminalized in 11 states which means you can be caught in possession of less than an ounce and you will only be fined around 100$. Since 1975 states have slowly been decriminalizing it i'm thinking within the next 10-15 years marijuana should be decriminalized nationwide that would be a huge load off of every marijuana enthusiasts back...hehe.