Hi,
The thing with Raw is that processors change and you can glean improved results later on. Not so with Jpegs. I began with a Kodak DCS 460 which is Raw Only and Photoshop 4 with a plug-in. Later versions of processors greatly improved what I got originally. Same for the other Kodak and Nikon and Canon models over the decades.
I think that is where the Only Raw mentality comes from.
Stan