What on earth is wrong with reading

non-fiction as a child?
I have been pondering this ever since Nicola Morgan wrote about it on her blog and on An Awfully Big Blog Adventure. Needless to say Nicola sees nothing wrong in reading non-fiction!
I read non-fiction as a child. I read a lot of non-fiction as a child. I read anything that came my way. Some of it was probably quite unsuitable. 
I remember a book my parents had. It was called "Heredity and you" and it explained, among other things, why brown eyed parents could not have a blue eyed child - or was it the other way around? I can't remember now. I read the entire book. I doubt I understood it all. It was an adult book and I was around eight or nine at the time.
My brother and I used to get non-fiction books in those wonderful packs from the Country Lending Service. I remember learning a great deal of history that way. (It was just as well because, due to the peculiarities of the rural education system, I only studied Australian history until I was fourteen.) I also remember many science books - and trying some of the "experiments" in the books that described such things. My brother and I made "telephones" and "parachutes" and kites and all sorts of other things from reading non-fiction. 
There was a series of books about composers which had small pieces of music in them. Before we had music lessons (music theory in my case but piano for my brother) we tried to learn to read the music and find it in our parents' record collection.
We still have Eve Pownall's "The Australia Book".
I was in our local library a couple of days ago. There on the "new books" shelf was a book I recognised. Someone else was just reaching out for it with a delighted squeal, "I remember this!"
The next minute she was sitting on the floor with two children reading Miroslav Sasek's "This is London". The were a number of these books, London, Paris, New York - and one about Australia. I know we got one in one of the CLS packs. It was pretty new at the time - and now, half a century later, it has been reprinted. It is still a good book.
Of course good non-fiction can excite the imagination. Of course it can make us dream and empathise. Will someone please tell me why anyone would want to stop a child from reading non-fiction?