That's not necessarily true. If your organization has tens of repositories with multiple important branches in each, all odds that at least some of those branches are lost.
Proper backups of all repos are an answer, of course.
The way we use git, master has everything that is production with short-lived feature branches for development work. Not needing to worry about git backups is perhaps the least of the benefits of this approach (and no real drawbacks as far as I can tell).
Proper backups of all repos are an answer, of course.