This. An example. My homelessness, caused by my disability making me poor, is illegal in many places.

The second one feels like a major part of the puzzle here. Poorer criminals tend towards more 'blatant' crimes, the kind that usually bring the police down on them hard (burglary/robbery, assault/murder, dealing drugs and controlled substances, etc). A wealthier criminal seems like someone more likely to be doing things that are harder to convict for, like fraud or tax evasion or something.

It takes more work to arrest and convict a Bernie Madoff/Sam Bankman Fried style than a street mugger, and the latter type of criminal is probably more likely to be from a low income background.