I thought they do use RICO against street gangs. Do you know the documentary series "Gangland"? In almost every episode it's the same story: a gang wreaks havoc in their city, the police try to do something, but almost always fail miserably due to the gang's capacity of "regeneration" and replacement of the arrested members, so at the end they call the FBI and a RICO case gets made with dozens of gangsters being sent away for a long time.

Willie Marfeo to Henry Tameleo:

1) "You people want a loaf of bread and you throw the crumbs back. Well, fuck you. I ain't closing down."

2) "Get out of here, old man. Go tell Raymond to go shit in his hat. We're not giving you anything."