Wasn't banks pretty clear that the Culture was his attempt to come up with a society that is as "good" as possible - if nothing else to provide a suitable employer for his supreme military genius (who I shall avoid naming).
Edit:
CNN: Would you like to live in the Culture?
Iain M. Banks: Good grief yes, heck, yeah, oh it’s my secular heaven….Yes, I would, absolutely. Again it comes down to wish fulfillment. I haven’t done a study and taken lots of replies across a cross-section of humanity to find out what would be their personal utopia. It’s mine, I thought of it, and I’m going home with it — absolutely, it’s great.
Edit:
CNN: Would you like to live in the Culture?
Iain M. Banks: Good grief yes, heck, yeah, oh it’s my secular heaven….Yes, I would, absolutely. Again it comes down to wish fulfillment. I haven’t done a study and taken lots of replies across a cross-section of humanity to find out what would be their personal utopia. It’s mine, I thought of it, and I’m going home with it — absolutely, it’s great.