My brother-in-law psychiatrist characterizes a lot of what he sees in his rural-ish poverity-ish as "piss-poor coping skills".

I've met people with IQs below 70 who were able to hold down jobs quite well (with very nice earnings records). It depends on the level of skills training. I've met illiterates with significantly higher IQs.

And it's not "poverty" per-se in the United States, which tends to have relatively wealthy poor. It's more social-emotional environment. For example, abused children don't do well as adults.