Autosave always uses the current filename, which is a disaster: the file is then saved in a state that you haven't chosen — probably many edits away from the file you want to retain. Microsoft Word, etc., do this best: you get regular files identified as "autosave", and you can continue working on the current file until you're at a point where you actually want to save it under the current name.
Some of us work by saving regularly, with updated names: Image1, Image2, Image3, etc. That way we can always revert to a certain precise point. And since you can't turn off autosave completely in this app, you're constantly getting a version that you don't want.
Not everyone will need this, and some will find it confusing; hence it should simply be an option.