I don't know that 'one of the main reasons' is fair. For profit prisons are vile cruelty-factories and have pull with lawmakers, but they hold less than 10% of incarcerated individuals. It's a reason, sure. But a main reason?
I think there are two obviously larger reasons:
There are more homeless people and homeowners see them. If you're a local politician, you can get very far by promising voters that they won't have to see homeless people. Here in "oregon, tolerant oregon" (to quote jello biafra) this is the most common sentiment to hear, and is reflected in policy.
Growing resource pressure leads to a rise in 'punching down'. As climate crisis, imperial turmoil and the rich taking ever more resources fuel poverty and scarcity, the social pressure to distinguish yourself from those further down the social ladder increases. Hating the weak identifies you as strong, which grows in value as more and more insecurity plagues our society.
existing wrongly (lemmy.ml)