Perhaps if you're driving, the things around you need to give you time to react to other things around you. Fewer things are more frustrating than getting honked at because you pressed a button, then got distracted by a car pulling up which you needed to look at to be aware of, then missed the printer asking if you want a receipt, and then having to press another button to talk to someone to ask for a reprint which, of course, holds up the line of cars growing behind you while someone gets paged to come to the kiosk.