The image name is often not useful at all. (E.g. something like shutterstock_1073920454325.jpg.) Futhermore the filename can’t even be changed later, since a new filename isn’t accepted, as an image already exists in the database using the same SHA1.
Given that not many people know about this, the first PR above adds the image alt as a fallback before defaulting to the file name. It being a fallback means that if a title is there, then it’s respected, if not, we use the alt.