@p Yeah Adobe did it because they are Pond Slime looking to lock things down, GIMP did it because... uh.... frankly... I don't know what possessed them to do it. Their "native" output should have been TIFF.

I did find out from Judge Dread that Photoshop started out as an in-house ILM software that they sold off for quick cash. It then near single-handedly built Adobe's empire - and they quickly supplanted the (shitty) behavior of Quark with their own flavor as they took over desktop publishing.

In the mid 90's there was so much goodwill towards Adobe and everybody hated Quark Inc with their stupid keyboard dongles and USB security fobs.

I guess they lived long enough to become the villain.