Thats a good observation. At one time it did seem that a lot of guys thought to be connected were burglars or armed robbers, possibly extortionists, some of whom might commit violent acts to climb the ladder of OC

And it seems like the burglary route is probably a less viable option these days due to cameras and other technology
How many burglaries can these guys commit before getting caught these days, and how many keep cash laying around these days for burglars to steal
Even with the drugs,they might get away with it longer,but then do a lot of time when they are caught.
And once they get a record,they are more likely to cooperate the next time they get caught.

Maybe before the 1960s or 1970s there were more lucrative, less risky ways for associates to get by financially.
The days of Prohibition and days before legal gambling for example.
And in those days it might have been easier to corrupt politicians and police to avoid prosecution