The illegal drug trade is the main cause of modern crime. From prostitution to muggings, to burglaties, to drive by shootings, to the billions spent by the tax payers to 'enforce' the law and all to no avail.
A section of society wants to do drugs... it's that simple, now if they're the ones that pay the taxes, then rightly, they're the ones that should benefit from them. Bear in mind that the average tax payer will save money, because all the billions spent by law enforcement against drugs crime will suddenly become available for other uses, such as education and health.