I was reading in the NEC handbook and the word "Usable" was written in there under the writer's comments.
We all know the code, but why would we need a receptacle in the toe kick if there are other wall outlets in the room? Vacuuming? or night light? You can't put a table or chair in front of the bookcase can you?
How about a large screen for the media center? An outlet right in the middle of the screen might ruin the picture.