The demand for alcohol contributed to the failure of Prohibition in at least two ways.
First, the demand for alcohol reduced people’s support for Prohibition. They knew alcohol was illegal, but they wanted to drink. This meant that they had to disobey the law. Because the law prevented them from doing something that they wanted to do, they stopped supporting the law. When people do not support a law, it is hard for that law to survive.
Second, the demand for alcohol contributed to the rise of organized crime. Since so many people wanted alcohol and there was no legal means to get it to them, people had to come up with illegal means. The people who were best at getting alcohol to consumers were organized crime gangs. They got rich from Prohibition. This contributed to the failure of Prohibition because people were upset that the gangs were gaining power. People were particularly unhappy about gang violence like the St. Valentine’s Day Massacre in Chicago. They were less willing to support a law that created opportunities for mobsters.
In these two ways, demand for alcohol contributed to the eventual failure and repeal of Prohibition.