Two different tools for two different problems.
WHAT BACKUPS DO
Let you return to a previous state after something went wrong.
WHAT VERSION CONTROL DOES
Records every change, who made it, and why, and lets you inspect and reverse individual changes.
WHY THE DISTINCTION MATTERS
A backup restores everything to a point in time. If you want to undo one change made three weeks ago while keeping everything since, a backup cannot do that.
Version control can.
FOR CODE
Use version control. A repository is a complete history, distributed across every clone, which is also a form of backup.
FOR CONTENT AND DATA
Use backups. Content in a database is not suited to version control.
FOR A WORDPRESS SITE
Typically both: the theme and any custom code in version control, the database and uploads in backups.
THE PRACTICAL POINT
Having code in a repository does not mean you have backups. The database and uploads are not in it, and they are what you cannot recreate.
WHAT NEITHER REPLACES
Testing that you can actually restore.
