It looks as though you have instructed Scrivener to back up your projects to your Dropbox folder. You can check the designated location by opening Scrivener’s preferences. selecting the Backup pane and looking at the file path listed at Backup location.
If your backups are stored in the same folder as your live projects, you should change the backup location. I would never store backups in the cloud myself (as in have that as my only backup location), but that’s a personal preference.
Don’t you mean you never store your live projects in the cloud?
That aside, I have my live projects stored variously in Dropbox or Sync, with zipped and dated back ups for frequently used projects stored in Box Drive, and less regularly used back ups stored in iCloud.
I also clone my internal drive to an external drive virtually every week.
But you should never have your live projects and your back ups in the same location.
They are backups, copies of older versions of your project, made for safe-keeping, usually every time you close the project (depending on your setting in Preferences). So if something goes wrong, you can go back to a previous version of the project.
You should check your setting in Preferences -> Backup and also read about it in the manual so you understand what you are doing.
Two of the beautiful things about Scrivener are its automatic saving of the working project and its automatic backup routine.
Open, write some, wait a few seconds, close the project, and all you wrote is safely both saved and backed up.