No, they are destroying them because that’s the way that they can keep a digital copy legally.

This is not true. Google Books does not destroy books. No court has ruled that you must destroy books to legally keep a digital copy.

	▲	tingletech 7 hours ago \| parent [-]
		I think under first sale doctrine you have a much stronger case with destructive scanning. Google Books, HathiTrust, and Internet Archive's book scanning project have had a lot of legal expenses.