So you could direct deposit your paycheck right in there and get the float on your CC payment and your mortgage payment up to the day that the checks were cashed. I think that they still have check writing, but the reliability of the US postal service is a bit crazy to rely on now either way.
My dad was a master check kiter (not sure that they use that term anymore) as we were poor and had little money and it was his way of stretching cash when there was none - he would just go back and forth between the banks, not really stealing money, just buying time.