I think you're missing 5) Because it is hard to find a reliable 2nd job where the hours do not impinge on a 1st job, especially when low-wage/unskilled jobs te

I think you're missing 5) Because it is hard to find a reliable 2nd job where the hours do not impinge on a 1st job, especially when low-wage/unskilled jobs tend to schedule in ways to make having a 2nd job difficult (e.g. not consistent, last minute changes, etc). 6) Because it is harder for some to find as many unskilled jobs as most due to their age, race, or education.