Legalize, regulate and tax all drugs that are currently illegal. Move it all out of the justice system and into the realm of public heath. We only made most of these drugs illegal in the 1960s and 1970s to create a vast and costly, but job creating criminal justice system.
Sure, there would still be a black market but not nearly the size of what exists now.
Oh, you want to buy the killer drugs? Sure, sign this Do Not Recessitate paper....

Easy answer because they benefit from the cartels and the money involved. As someone already said you want to get rid of them the only way is to legalize all the drugs that they make money from then deal with the inevitable fallout of addicts and their problems.

One problem gets exchanged for another, it just depends which one is easier to deal with.