Prohibition did not make the consumption of alcohol illegal, only the manufacturing, distribution and sales of recreational beverage alcohol. Anyone could make their own and consume it and even freely share with friends.
According to Havard reserchers and the data, Prohibition did decrease use by up to 30-50%, decrease medical complications, and alcohol-related crime. Violent crime and homicide did not increase during Prohibition but was steady.
A black market was created by organized crime but revelations about J Edgar Hoover's FBI demonstrate that he was covering for the mafia (also serious undisclosed morality issues) and publically denied its existence until the Apalachin Meeting embarrassed the FBI in 1957. The media also had a hand in sensationalizing the impact of the mafia and crime.