This is the actual answer. If you want a computer to power itself off, you either need to design a contraption that mechanically opens a power switch, or you n

This is the actual answer. If you want a computer to power itself off, you either need to design a contraption that mechanically opens a power switch, or you need a transistor that is carrying the full load of the computer at all times. It's much easier to have a switch for the human to press.