So either you do not use the graphical UI for backups, or you do not verify your backups. In the UI, the latter requires to start over the whole procedure again in 5 hours, which is extremely annoying and why I make backups less frequently than I should.
Which is why for most users this is too inconvenient. I’m fine with the command line, but even I can’t use it for everything. It takes time to learn new commands (there’s always too much to learn) and new users won’t be able to start doing it immediately, loosing precious time and risking their data.
This tells more about your specific users than the general situation. Backups of whole qubes helped me many times when qubes stop booting or I want to clone my installation to another, independent device. Also when I upgrade to a new Qubes version. I love that I don’t have to make any in-qube configuration and all installed software just works immediately after the restoration. The disk space overhead is tiny and the restoration process is straightforward. I’m happy that Qubes chose this direction by default.