Cache: directive is very useful for many circumstances, especially for information archiving purpose, what a shame Google even want to cancel it.
(The Internet Archive can't be counted on to remain unchanged either, but at least the Internet Archive will either remain unchanged or disappear, never change. I wish archive.org didn't auto-nuke entire sites based on robots.txt, because when domains disappear the domain squatters often seem to use robots.txt files for some reason.)