Neither do I.
Of course they wouldn't go out & get a real job. But, legalizing drugs would remove their source of income. Dealers are the only people in the 'hood with money, power and prestige. Remove that and they become just another group of derelicts, with no power to attract recruits into their fold.
We can preach to inner-city kids all we want about how the road to success is to get an education and a job, but when all the real life successes they see are people who dropped out of school to become criminals and drug dealers, they are smart enough to follow the proven route...
When you say "legalizing drugs" you mean all drugs, including prescription drugs, to all ages. You do realize that any drug not legalized will be sold to all ages by the gangs. Legalizing all drugs is not a real high priority for oh, maybe 99% of the American people.
Assuming we did legalize all drugs, gangs would simply get into the exporting business, reversing the current pipeline, illegally exporting our legal drugs to countries where they remain illegal.
Or they'd get into smuggling cigarettes, people, human organs, guns, whatever. What they will NOT do is get a real job.