There are many, many more cases where the user doesn’t expect the name to become public when he sends a photo. If I send you a photo of a friend that doesn’t mean I want you to know his name (which is the name I gave the file when I saved it)
In fact, I often refer to the name of the photo in the body of the email (e.g., "front_before.jpg shows the front of the car when I picked it up, front_after.jpg shows it after the accident.")
I imagine this is an extremely common use case.