A very broad questions and not sure what you mean. MJ affects Society in numerous ways -- both negaTIVE AND POSITIVE. Some negatives may include-leads to other illegal drug abuse,impaired driving and impaired people are dangerous,increase crime,cost,dependency,have no standard for the amount of THC that is in one variety to another can cause problems/potency), carcinogenic pathogens have been found in MJ,violence. Positives can include , tax revenue source,medical affects for pain ( medical use of MJ), suggest you research this thoroughly. Not sure if it would benefit Society to have more people on MJ, and that 's what you would get if restrictions were taken off. Keep in mind that a lot of my answer is based on opinion and background of substance abuse research and law enforcement experience.
I tell you it has been answered for a full government break down. Search Schafer commission 1972, Nixion's administration gave him this report before he started the so-called war on drugs.He just threw it in the trash and went ahead with it anyway.