One of the reasons is: They can't trust the police to come out and take the people who cause trouble out.
Neighbourhood gangs, esp in chicago are territorial and they try to "protect the neighbourhoods." (I think they do cause more problems) This came up during the riots earlier this month. The police were stretched way too thin. Gangs did stop the looters and rioters from extending into their neighbourhoods. (Deeper within Logan Square and Little Village were an example)
Neighbourhood gangs, esp in chicago are territorial and they try to "protect the neighbourhoods." (I think they do cause more problems) This came up during the riots earlier this month. The police were stretched way too thin. Gangs did stop the looters and rioters from extending into their neighbourhoods. (Deeper within Logan Square and Little Village were an example)