Uneducated, poor street hoods, as a group, generally arent up on things like engineering, physics, large group cohesion and social engineering, etc needed to fly and operate and maintain an advanced combat spaceship.
Convincing angry, uneducated, disenfranchised youth to perform various street crime is easy. Having them serve as skilled, disciplined crews of a state of the art warship is likely much, much harder without them losing the very elements that make them a street gang in the first place.
Can you take street gangers and turn them into soldiers? Sure, happens all the time, but generally they stop acting like hoods and start acting like soldiers. But taking say the Gangster Disciples and trying to get them to operate high end combat aircraft would likely end disastrously (and humorously).
Are there criminal organizations with that kind of technical know-how in real life? Sure. But the organizations who do are much more sophisticated than the typical gangbanger set. The South American cartels are chalk-full of former military and dirty spec ops types, the Russian mafia is full of former KGB and GRU operatives, etc.
Even the street hood who fights from the ground up rarely holds onto gangbanger mentality after he "makes it", in fact it was likely his ability to look beyond the limited world view of being a street hood that helped him advance in the first place.
Basically, if a gangbanger had the technical, scientific, and social skills needed to be an effective crew member of a combat spacecraft, he or she would likely not be a gangbanger anymore. They would either graduate to the upper echelon of criminal organizations (i.e. RL Mafia, EVE Guristas, etc), or they parley those skills into a productive career as either a legit military personnel or something more conventional that likely pays better and less likely to get them shot.
Short Answer: EVE gangbangers exist....probably in the untold billions. They probably serve as street muscle for the various syndicates. They just dont pilot or crew warships. Theyre pawns, not kings.