Not always useful if e.g. you're locked out of the BIOS, the setting constantly auto-resets for no apparent reason, the keyboard is partially broken.

The sad thing is that I've personally experienced all three of these problems. #%^$ whoever decided that the Function keys should be brightness etc by default.

But it's also not the default (at least on OSX).

'It's not the default' is a terrible argument in a thread specifically about customising vi to the Nth degree ;)