Ultimately, FDIC insurance is a function of a traditional banking system that borrows and then loans out its customers' money on mismatched time horizons.
Banks make money by using the funds in customer deposit accounts to make long-term mortgage loans and charge interest on them.
But... What if all that money is tied up in 30-year loans and everyone wants to withdraw it today? That's called a bank run and that's the problem FDIC insurance was created to solve.
If, like PennyWorks, you don't have that problem in the first place, then FDIC insurance isn't really a thing. We don't engage in mortgage loans, which are a big driver of that timing mismatch.