That's utterly silly. If you take yourself seriously as a graphics editing program, then inevitably you have to move to one format that you can then convert into others. Otherwise you have to implement every single operation on every single file format you support. With the One True Format, (.otf) you can convert your .jpgs to the .otf and then do the operation there.
This then presents a problem. Tech-savvy users know that there will be a loss of data when you save to a consumption format. But the rest of us don't. If you allowed open and save in the same format, people will make the intuitive leap, that they're actually editing the files in that format, when they're not. They'll think all the layers they made will carry over into the PNG and that they'll be there when they re-open the file, when in fact they won't.
It would be a nightmare, because nobody will know what will save and what won't. You'd have to then educate users that to get everything to save properly, you have to save to .otf. Or you could just bake that logic directly into the app.
I know users don't read, etc, but the trade you're making is that the simple process of editing a file and saving it is now much more annoying. I just want to make changes to my PNG, not deal with the One True anything.
The stated goal was to make it harder (still? I guess people clicked through the warning without reading) to accidentally save in .png or .jpg and lose the layers. But the result, for someone whose usual workflow is to open a .png/.jpg, edit, and save back to .png/.jpg, could not be more user-hostile and obnoxious.
In response to a complaint, someone on the forums wrote:
> This is the way Gimp now works. Of course you can consider this a PITA. But for other folks, losing work because they saved as JPG instead of XCF is also a PITA. The philosophy is that people that are impacted negatively by this change are people with very simple work-flows who would be better off using simpler software (XnView, Digikam, Lighttable...)
In other words, all of you people with simple workflows, that worked just fine in Gimp for years? Now you have to go off and learn some new software, because Gimp is for Serious Graphic Design™ only. Ugh.
I got excited researching this because I found a changelog for Gimp 2.8.4 that mentions patching the behavior to be sane, but then I realized that's only a patch in the unofficial OS X build. On Linux, the same nonsense in the latest version.
Every program I use saves to the original format by default, most warning you if there will be data loss. Whether you like it or not, this is how software works and how users expect it to work. If you want to automatically backup a different format that's fine.
GIMP should have option "also save as native format in image repository" that is on by default, if the developers care so much about the conversion losses.