It's not the demand for the drugs keeping the cartels in power, it's the prohibition of these drugs that's driving the prices up and allowing the cartels to prosper.
The opium poppy is a weed, can grow practically anywhere. Coca bushes are common, and could easily be a simple cash crop like coffee in South America, except for the global ban on cocaine.
De-criminalize the product, the criminal gangs profitting from them vanish.
Now they're trying to blame guns, instead of the wrongheaded drug policy.