Because only 1 in 50 people can think for themselves and are willing to be responsible for themselves, and is also willing to leave other people ALONE.. Everyone else wants to use govt FORCE to take things from other people, or make them live as the forcers wish them to live. Whether its laws against guns, booze, gambling, prostitution, abortion, or dope, those laws are inherently wrong, because they interfere with free choice, about subjects that are nobody else's business. You of course should have laws against the MISUSE of arms, just like you have laws against murders, even if they are committed by strangulation. If the doper neglects his kids, you lock up for the neglect, not for simply possessing the dope! or selling it, growing it or making it.