Because the WoD and opposition to drug legalization benefit the same group, the drug dealers. If you want to control drugs and drug use, legalize it and let the Government over regulate it like water rights. Now that would hurt the criminals.
Right now there is nothing stopping a 14 year-old girl from buying Marijuana or Cocaine. Drug Dealers don't require ID and the payoff out weighs the threat of Government action.
Did the household survey require respondents to take drug tests to prove that they didn't use drugs or were they just taking their word for it? As all the popular theories about drug users say, you can't trust them to tell the truth.
Ironic, that libertarians want "small government," but want the government to regulate drugs. Rather, hypocritical and revealing.
Drug dealers or no drug dealers, legalizing drugs will and has increased drug usage, including usage of harder drugs. Considering that 26-29% of all murderers were high on drugs and that up to 70% of all criminals in prison were high on drugs, legalization would be result in a dramatic increase in crime.
Further, we already lose more people each year to drunk driving than to murder. Why need we need more losers using drugs, intoxicated and killing innocent people.