My impression has been that the capitalization is to identify the word as an image format (a stand-in for whatever actual format is used), rather than being an initialism. Canon, Nikon and Sony among other hardware and software companies use it in this way.
ZIP similarly doesn't stand for anything but is styled as such. So I suppose the pushback is more against being used as a stand-in for generic raw image formats.
Edit: just noticed your comment was greyed but I didn't downvote it fwiw.
You can also find tons of instances of people referring to Apple's computers as MACs. And that one is even worse because MAC is an actual computer-hardware term.
So "RAW" may not be a well-known acronym, but it doesn't mean it will never be.
The Brits suffer from the opposite problem: making acronyms into regular proper names. It's endemic over there; their articles are replete with references to the nonexistent "Nasa," "Nato," and other entities. In at least one case in the last few years they did this to a piece of legislation where there was actually a British company with the name they were misusing.
ZIP similarly doesn't stand for anything but is styled as such. So I suppose the pushback is more against being used as a stand-in for generic raw image formats.
Edit: just noticed your comment was greyed but I didn't downvote it fwiw.