Eventually computers began being able to turn themselves off.
Does anyone know what prevented older computers from doing this? And if it was possible, why the design decision was made to make the users turn the computers off themselves? Was it some sort of "feel in control of this new thing in your house" thing?
Your master power switch was actually just that, a master power switch within the power supply. Your computer was shocked to life by having this switch turned on, and your computer was turned off by literally having this turned off.
It was just easier to design around this. Also bios functionality was incredibly limited at the time, normally being configured via DIP switches on board and hardware control via OS was a long way off, typically the only hardware control was to assign interrupts and handle them.
In WinNT 4 the same text is displayed in a window. Though, afaik it is displayed by kernel mode and not from Win32 subsystem.