It's one of the things IBM's David Bradley will always be remembered for. Before that, whenever a program crashed the machine, you'd have to hard reset the thing, which was arduous and slow in those ancient times. Originally meant to be ctrl+alt+esc, he found it too easy to bump, so tried ctrl+alt+del instead, which was harder to bump in those days.
Ctrl+Alt+Del, IBM invented it, Microsoft made it famous.