I'd say 80% of the books in our house (home learning resource or literature) are wrapped up; with the exception of hard cover books.
I guess the obsession came about when I saw dog-ears on the books and it irked me. Besides, the kids don't really handle the books very kindly so wrapping the books up would be a safer bet for me.
So now, all new books that I've purchased are nicely wrapped up! *lovez*