Banks don’t “guard your money” at all. They use it to make loans. Leaving money at a bank exposes you to vastly more systemic risk than just putting bills in a safe or something. If they’re not remunerating you for it, you’re getting screwed.
This is very dependent on the country you are in. Some countries have very conservative risk tolerances for their banks which are imposed on them and watched closely.
With central banks the risks of loss is low enough that nobody needs the just keep my money safe service anymore - except now they do because rates are so low