Because it's not an online backup. The canonical version of the photo now lives on in a remote service, managed and maintained in perpetuity by someone else.

Because it's not an online backup. The canonical version of the photo now lives on in a remote service, managed and maintained in perpetuity by someone else. The user's local computer has become just a cache. This a fundamental shift in how people use computers. I think it's reasonable to assign that shift a label, and that label has turned out to be "cloud." (No argument that the term is overhyped and overapplied.)