This prohibition was enacted during the Great Depression, due to concerns that large money center banks might have earlier bid deposits away from country banks to make loans to stock market speculators, depriving rural areas of financing. It is doubtful that the rationale for this prohibition was ever valid, and it is certainly no longer applicable.
Today, funds flow freely around the country, and among banks of all sizes, to find the most profitable lending opportunities, using a wide variety of market mechanisms, including the federal funds market. Moreover, Congress authorized interest payments on household checking accounts with the approval of nationwide NOW accounts in the early 1980s.