I don't remember which book it was in, exactly, but there is a conversation at one point with a Culture guy who is waiting tables, including cleaning them. He explains that a lot of humans actually do this kind of stuff, or, say, constructing spaceships, as a background from their "real" job-hobby (which is usually research or art) simply because completing things makes them happier, while cheerfully acknowledging that none of human labor in Culture is meaningful in the sense that it couldn't be done better and faster by machines. But it's still meaningful in a sense of giving people meaning.
