I don't know, I think manky toilets would fairly put a bit of a blight on the finest of dining experiences.

That does sound a bit like hiding one's light under a bushel though. I guess people have an expectation (reasonable or not) that the quality of the food will be roughly on a par with the setting, so from a business point of view it doesn't make sense for it to be surprisingly better. (But that's still strongly preferable to it being surprisingly worse ;-)