One benefit to the bank is that they can apply the transactions in whatever order they want to your account. Banks like to apply the largest debit first, so that maybe all of the smaller ones will cause an overdraft, thus maximizing the overdraft fees they can charge. The banks say they do this so your mortgage payment for example doesn't bounce, but it doesn't hurt that they make a ton of money from it - not that a bank would ever do anything just for the money.