Note that I said “a part” of a backup strategy.
Become a Patron of Ask Leo! and go ad-free!
Why only part?
SyncToy only copies the data files that you tell it to copy. No more and no less. For instance, you can’t use SyncToy to backup Windows itself.
And in this case, SyncToy only runs when you tell it to do so. It’s possible to schedule it using Windows, but scheduling is not part of the utility itself.
Making backup files or backup copies of files can be a very useful part of a backup strategy.
A utility like SyncToy can bundle up a number of manual steps into a single run of the program. Say you work on documents in My Documents. You can have SyncToy automatically copy anything that changed to another folder on some other drive. It may be your external backup drive; but after setting it up, you have to remember to run SyncToy or walk through the steps to schedule it using Windows Task Scheduler.
As long as you realize what you are and are not backing up, and when you are and are not backing it up, tools like SyncToy are great. As a matter of fact, they’re so great that years ago, I actually wrote my own command line utility that is very similar. And it’s something that I continue to use to this day.