A lot of folks like to condemn interest as usury, but there are reasons for a lot of it. Inflation means dollars tomorrow are worth less than today. Credit card infrastructure costs money to install and operate. People default on debt, leading to outright losses or added costs for prosecution. And, of course, corporate greed isn't a fantasy.

On the other hand, interest rates are a price for money over time, and as you noted, price signals matter. When government sets an arbitrary cap, no matter how "reasonable" it seems at a glance, it distorts the market and alters consumer behavior while changing the incentives for production and investment.

No matter what school of economics you explore, you find almost universal understanding the price controls are always destructive. The exceptions usually just mean arguing that in a particular pet case, it totally doesn't matter because.... Look over there, something shiny!