:-)
Though to be fair it doesn't answer the last part, of why they are not on a desktop PC keyboard.
to which the simple answer is, you haven't got a multimedia keyboard, if you did have one then most of the same controls would be on it but they'd be on their own keys (due to having more space available). the brightness wouldn't be on there as that is adjusted on the monitor, not the computer. (and on a laptop obviously the monitor is part of the computer)