> Why does this idea bother humans us so much?

I dunno; it doesn't bother me at all.

What bothers me is pretending that the Culture is humanity's. Or that humans are in any way relevant to the whole plotline. It's like if somebody rewrote all the great works of literature from the perspectives of the protagonists' dogs, and then threw away the originals, and pretended that this was somehow a useful perspective. That would bother me.