Now you're just talking out of your ass. First off, you can't claim that it worked as intended even if everyone stopped drinking but the adverse effects crippled the rest of society. Second, people only stopped drinking until the market (black market in this case) had time to adjust. The cost of alcohol spiked through the roof, alcohol related deaths remained unchanged, alcohol consumtion relatively unchanged and crime spiked.
http://www.nber.org/papers/w3675.pdf?new_window=1
---------- Post added 2012-10-24 at 01:01 AM ----------
If hard drugs were legal, there would be much fewer sources of easy criminal money. Additionally, if "pure" drugs like cocaine were legal, there would be little demand for the more harmful variants or harmful drugs. Crack, Crystal meth, etc, all redundant. Why? Well because the only reason they are consumed today is because the "pure" stuff is so expensive. With legalization would come quality, safety and lower prices.