re: Current Mortgage Rates

Because most banks require a certain amount of waiting time on a borrower who has a rate locked in the market to relock. They will base it on worse case pricing if it expires between then and the available relock period. It’s to deter the availability to lock in a position over and over again if rates got better. If no one executed their positions locked in with the institution buying the security there would be no market. Or really it would just drive up the cost of lending which in turn would be passed onto the borrower.