I think skore's point is right though: reminding users to make backups is the lesser evil.
Time Machine isn't going to stop someone who places value on doing proper backups from doing them, and if it makes it easy enough for my mom do back up her files, then that's a net win — not marketing.
And hey, it only took me reminding her 5 times before she got the external drive and set up Time Machine — no family tech support involved.
The central problem with backups is that no one makes them but everyone should, without a question. That’s an attempt to solve that problem, even going so far as to purposefully annoy people! (Remember, everything is a trade-off and usually you will never be able to make everyone always happy.) This dialog box is the furthest thing from a marketing gimmick I can imagine. It’s comically far removed from that. (And, I think, exactly the right move. Yeah, people who know about backups already probably will not use Time Machine – but for everyone else that is pretty great!)
If I had to, gun to the head, I'd say that no one ever was.
I seem to remember that Windows pops up a baloon in the system tray every once in a while nagging you to configure the system for regular backups. That seems much more sensible.