Photos never changes the original file, so its file type will never change. Pictures you see on the screen are not files, so there's no file type. For edited pictures, Photos just remembers the editing steps that you made. So no edited picture is saved, and there's no file and no file type there.
When you need an edited picture, Photos reapplies the editing steps you made to make a new file-- that's what Export does, and that's where you have control over the file type. And that only makes sense when you are saving a file for use elsewhere.
Except for the original file, there's really no file types in Photos, and access to pictures has nothing to do with file type. There's no advantage to file types until you Export.
Where do you think that you need easier access?