I have no numbers to back me, but my impression is the vast majority of OS X users can't be bothered with doing backups even with a built-in Backup solution, much less a 3rd party one.

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.