There are backups and there are backups.

For some people, like yourself, archiving backup is the one true backup, while others make do with rolling hourly/daily/weekly backups or even something as rudimentary as copy-pasting folders by hand. Ideally, yes, everyone should be doing versioned backups to a zfs storage cluster. In practice, no, lots of people have just enough motivation to get an external drive and start making copies onto it.

That said, I am planning to add versioning and I am looking at adopting git's packfiles for that purpose. The idea basically is to use an open format for storing archived versions, so not to lock in the users. This is in its early stages, so it may or may not work out.