The same reason we walk up to where people are waiting for the elevator with the button already lit---and press it again.
theyre hoping that they can reduce the resistance with harder pushes or theyre under the delusion there is a dynamo beneath the button
to see if it will work one last time before they have to walk into the hall way to get the batteries
*throws remote across the room*
because deep down we are all just monkeys
maybe they're frustrated