Nixon started the War on Drugs because he couldn't declare war on black people and hippies

Only within the granted powers defined in it.

It is also very arguable whether drug prohibition has done anything to promote the general welfare of the people. It’s been nothing but destructive. People want to use drugs and trying to stop them from doing sop hasn’t done anything to stop them or had any positive consequences. It’s only made violent criminals rich, sent money to enemy threats, put people in jail, made the drugs more dangerous through lack of purity controls, and increase the associated crime and negative effects for both the user and the people around them. Not to mention brought about a rise in newer and less studied drugs that are more dangerous than the ones they try to mimic. The whole bath salt and spice fiasco was directly the result of prohibitions from allowing people to get the drugs they wanted and to circumvent drug tests. It’s been the biggest obstacle in drug harm reduction and people who want treatment to quit from getting a quality treatment.