Please clarify the purpose of sync. I thought of it as a backup tool and reinstalled windows and now years of bookmarks are lost. This hurts!

I would like you to please verify the purpose of sync more clearly in the future. I had to reinstall windows and thought I could use sync to save my bookmarks. Now years of bookmarks are lost because the program was not specific in telling me about the recovery keys until it was too late. This put a huge dent in my productivity and really sets me back. I realize that nothing can be done at this point but please clarify this for others so that it doesn't happen again. This really sucks!