A second part of your privacy routine
Keeping photos private and keeping them recoverable are different needs. Backup helps you prepare for a device change or the need to restore your collection.
Check before you change devices
Review your backup status before replacing or resetting your phone. Keep your recovery information somewhere safe and make sure you can still access the Apple account used for iCloud.
Backup is different from sharing
Backing up your vault is for recovery. It does not mean you have chosen to share its contents with another person. Use the sharing feature when you want to send selected photos.