I think the joke is that Microsoft did do something very like this -- they call it Windows Recall -- and it got a lot of angry pushback. (Partly, IIRC, because the specific way they did it initially was very bad in terms of security and privacy, but I think a lot of people quite understandably don't trust them to implement it (a) the way they claim they do or (b) competently, so even after they made a bunch of changes aimed at making it less scary it's still viewed with a lot of hostility.)