Well, these days 22 years have passed since the original file format was designed -- and not by me, though I probably would have done the same thing, 22 years ago.
Also, it's zip + xml files + binary files, not all xml.
Well, we're not storing pixels in xml, but now we've got two xml files, one with author data, one descibing the image and a folder tree containing various kinds of binary data, all in a zip file. And yes, updating in place is a bother.
It's really hard to update in place, we basically have to rewrite the whole file after a change, and, of course, we've got to do a lot of things ourselves, like inventing an xml format for describing the image.
I was surprised, but also intrigued when I discovered that Manga Studio (Clip Studio these days) used sqlite for the native file format, including the pixel planes.
I wish my predecessor at Krita had made that choice, instead of choosing to re-use the KOffice xml-based file format that's basically a zip file with stuff in it. It would have made adding the animation feature so much easier.
Ah, no. Took me a couple of decades to learn to parse that, but, in fact, nope, it's not a solicitation for a preference, it's a direct command. Or, at least, it's been that every time someone has used that phrase at me.
Also, it's zip + xml files + binary files, not all xml.