I think I'm on your side because it's possible for anyone to understand how interest works and make these judgements themselves.

But a lot of people just straight up don't understand interest (despite it being within their capabilities) and e.g. make minimum payments on their loans and complain when the balance goes up. A particularly egregious case (because the people in question are educated) is when people make minimum payments on student loans and don't seem to understand why the balance is increasing.