There are a lot of crime groups based in poor neighborhood, for example, all kinds of street gangs, it seems most members of these gangs comes from a very poor background, like an immigration family. On the contrary, in some upper class neighborhood there always lack gang activities.
However, some groups, especially mafia type groups are different. Lots of LCN members are not from poor background. Im not saying their economy class is high, just saying that they are from some sort of working class neighborhood and I think LCN, bikers and some white racial gangs are similar in this aspect.
It also occur to me, some organised crime activities actually rely on middle class society. Well maybe those poor neighborhoods have the biggest drug market, but apart from this, things like gambling, loan shark, union corruption request you to have connections in some economically better area, I assume thats why OC groups and street gangs have different composition.