> But what I'm curious about is the causal difference between the two
A majority of personal bankruptcies in the US being caused by medical expenses might be a good place to start looking. You can be "broke" living paycheck to paycheck and "making it", but you're on even more of a razors edge than most. One medical emergency, one car accident, one removal of work hours etc and you start to fall behind, and that's when late fees and compounding interest work to make sure you never get out of the hole.
Thanks for being skeptical, looked it up because of that. Looks like the primary study people cite is this one, which indicates around 65% of people filing for bankruptcy cite a medical contributor of their bankruptcy. That includes medical bills (highest contributor overall) and loss of income due to medical issues.
While we are not at the same state in history, there is a reason why Usury was illegal in many societies. Interest on loans can end up crushing one part of society while enriching another that any feel didn't deserve it. It can actively produce inequality.
A majority of personal bankruptcies in the US being caused by medical expenses might be a good place to start looking. You can be "broke" living paycheck to paycheck and "making it", but you're on even more of a razors edge than most. One medical emergency, one car accident, one removal of work hours etc and you start to fall behind, and that's when late fees and compounding interest work to make sure you never get out of the hole.