Pushed by many upper-middle and upper class
Americans who could afford to stock
wine cellars. Many forces behind prohibition felt that while they themselves could handle alcohol, the lower classes were clearly afflicted by it, although organized crime and a large number of
teetotalers were also involved.
Prohibition caused many Americans to start drinking irresponsibly, drinking to get drunk, drinking in secrecy, drinking as a sign of rebellion, as well as preventing alcoholics who wanted to stop drinking from seeking help.
A really good book covering prohibition is Drink: A Social History of America, by Andrew Barr.