The increases in those neighborhoods is more meaningful to those who live there because they’re already low income and disproportionately more rent burdened. And because most of the area around there is zoned for single family homes(when not industrial) developing anything other than that (even just low rise apartments or other lower cost housing) is more expensive for the private sector because they would have to go through a long and expensive variance process, getting neighborhood feedback, etc.

part of the reason there hasn’t been expansion of trailer parks is because of our zoning as well.

Finally as someone else said, expanding supply of “market rate” housing in wealthier areas keeps rents from rising elsewhere even in low income communities https://research.upjohn.org/up_workingpapers/307/