The issue is deeper. War on drugs has created many little cartels, many of them don't make much money off of transporting drugs to USA. These local criminal gangs are there to extort money from businesses, kidnapping, selling drugs locally.

When PRI was in power, politicians and plaza bosses had mutual understanding: "you can transport drugs, but don't mess with locals who have no connection with drugs". Whenever USA tries to get rid of a kingpin, it will create more splinter factions, whose only way to fund themselves by kidnapping, ransoms, extortions, etc.