Well, compared to books which have public archives that pretty much receive one print of each book in existance, all of those dumps come from private people. Even those emulators are created by hobbyists.
And then there are the always-online / drm ridden games that are unplayable again.
Movies have the same issues. Lots of old movies have been lost to time, only the most popular ones have been preserved. Yet again, mostly by private collectors.