Re: I... Er... Um... Words fail me!
It saves on their bandwidth, because fresh Windows 7 machines tend to fall over while they catch up with all this lot on Windows Update, and because it's not a "Service Pack" they don't have to extend their extended support deadlines.
It's hardly a public service to their customers. It's a bandwidth-save on probably one of their highest-bandwidth services, using a technique that they've done for every OS they've ever released, at a time when Windows 10 is about to be become pay-only and the die-hards are making their system insecure because they won't touch Windows Updates because of Windows 10 at the moment.