Ignorance is part of it. Another part is that there's tremendous pressure on U.S. critics today to give positive reviews now that so many book sections have shrunk or disappeared. A lot of book editors take the view that they have so little space left, they want to give it only to good books. So (as I see it) there's a lot of spinning by critics: an overwritten book gets called "lush" or "lyrical." It's a sort of code.