Actually, I think Banks does address some of those points - mostly by pointing out that if you do have a society where almost all reasonable requests can be satisfied by asking then the perceived value of "owning" something becomes negligible. You could make unreasonable requests, say to have planet built for you, but you'd have to ask a Mind for that and they might or might not do it - depending on how interesting the request was. (Given that the Culture regards planets as bit wasteful from an engineering perspective, I can't imagine any self respecting Mind would build one).

Of course, the real get out, as Banks has pointed out a number of times - Culture people are not humans - they are the results of 10,000+ years of direct (genofixing) and indirect (their language Marain) manipulation by machines to be a good deal smarter, rational and more capable of enjoyment than we are. You could argue that this is the machine gods making their pets more compliant, or not....

Also, Look to Windward does mention "re-inventing" money... :-)