Age Ranges on Books?

Am I crazy to think this is actually a useful idea? Graeme Neill reports for The Bookseller that British publishers are going to put age ranges on the back of children's books beginning this fall. Age ranges are: 5+, 7+, 9+, 11+ and 13+/teen. Best of all, Neill writes, "Guidance levels will be the responsibility of individual publishers, and will be an indication of reading level interest rather than ability."

Interest instead of ability. Finally.
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Update: My smart readers have convinced me that I am, indeed, crazy (or, at least, naive)!