For me, it's a money management thing. There's also debit cards, checks/cheques (for some weird reason, Americans seem to love these. Considering you have to pay for them and not the bank, I don't know why), online banking (some of which are direct transfers some of which just print and mail paper checks), cash machines and for receiving money, direct deposit, cashiers checks (for when you don't want to carry large amounts of cash around)... There is no direct account-to-account available to the public (with my bank anyway) but this wasn't available in the UK when I left either. There's also no check guarantee cards so if you write a check at the grocery store, the person will take your driving license number and phone number. There's no chip and pin either, still regular old mag-stripe (though some cards do have RFID chips - look for the little logo. Though I have never seen these used *anywhere*)
The US consumer banking system, like its mobile network until recently, is antiquated.