I really don't agree. The keyboard and mouse are specific pieces of hardware and have very specific and quite common problems associated with them. This is particularly true of keyboard which is a nice, broad tag that covers such subjects as different keyboard layouts, shortcuts, remapping keys etc. These are classic issues that many users have problems with and for which the keyboard tag is useful.
There are 1,220 questions tagged with mouse and 1,705 questions tagged with keyboard. For both tags, more than half have been answered so I'm not sure I buy the "nobody's answering" them argument. In any case, even if it were true, I don't see how removing these tags would help get more questions answered. All it would do is further reduce their visibility.
Finally, both these tags clearly show what the question is about. Much more so than any of the alternatives you suggested (xorg, xserver, bluetooth, usb). If I tag a question with mouse, then everyone understands that it is about, well, a mouse issue. If I tag with usb it could be about any number of things. So yeah, the tags could even stand alone (though of course they shouldn't).
In conclusion, I feel both these tags are useful and should be kept around.