The computer should be coded to distiguish the difference between it not detecting a keyboard, and one not being plugged in. But the traditional IBM PC has a number of daft aspects to it that no one ever bothered to correct.
"I'd say it's the computer programmers who, from their ivory towers, seem to assume that everyone on the planet is totally computer literate! "
Well, back in the days (early 80s) when that message was created, that was pretty much the case.
If you're interested in antiques, I have a working Osborne Executive - the first portable, with 2 inch green screen and two 5 1/4 floppy drives. Runs word processor and spreadsheet - what more do you need!! :-)