Why would you need to if they're synced to the cloud, just download them again
General answer: Because it's needless complexity (relying on a company's service rather than... reading from a local disk) that masks what is actually happening behind the scenes. It will always be less reliable.
Answer in that specific situation: They were files in a OneDrive that no longer existed after a tenant migration (they hired a consulting company that seemed to bungle things).
If you set up files on demand, you have to demand your files, it's in the name.
Hope they never paid the consulting company