Yes, I understand that. But I don't understand why we couldn't have a system whereby, to cover payroll, a bank creates a loan to each company every payroll day

Yes, I understand that. But I don't understand why we couldn't have a system whereby, to cover payroll, a bank creates a loan to each company every payroll day, transfers cash to the (FDIC insured) bank accounts of employees, and then liquidates some of the company's T-Bills over the next couple of hours or days to cover it. That seems like a way of making sure everyone's paid without companies having to risk > $250k balances at any time.