You'll find a lot more multigenerational housing in urban areas seen here. For many that means the parents moved in with the grand parents who have held the house since housing prices were reasonable.

Additionally for poor people, family connections are much more important. Someone with a white collar job and good pay check can use PTO to take a kid to a doctor's appointment or if there's a snow day they can take off to watch the kids. Hourly or poor people don't have the luxury all the time. For them to take off a day they just won't get paid, so they'll rely on family members to help watch the kids.

The same idea holds true for needing to borrow money. People without lots of money are less likely to have credit cards or bank accounts so they rely on cash which it's much easier to get from a family member in person than hoping your letter makes it in the mail.

When you talk about moving a 'family' to a less hostile environment you need to consider that the immediate family isn't the only thing that would need to move. A social safety is a huge factor in whether or not someone stays and remains poor or has the ability to move out of that situation.