Why doesnt the US legalize narcotics?

It'd make perfect sense, seeing how the US government is incompetent on all levels and is too scared to disappoint Mexico by deploying the US military to the border to eradicate narco traffickers. But the US is more concerned about over seas wars. Just saying. What's the point of waging a war on drugs if you refuse to utilize all that's in your power? Mexico has tens of thousands of soldiers on the streets and near border towns.