Its the leftist way. They want to micro-manage society, but once in control, they are more puritanical than anyone.
My experience is with Communist China. When Mao took charge, drug dealers were executed on the spot, addicts were sent off to prison camps, where they either died or became clean, along with prostitutes and operators of bars and brothels. Homosexuals were jailed, and society called them freaks. They know exactly how society is disrupted, having promoted the disruption themselves, and being good Marxists, will allow no chance of it once they are in charge.
Same in Russia, Cuba or any other Michael Moore admired society.
One of the few cases of a successful War on Drugs. China had a serious problem with opium addiction before Mao came along.