After reading through more comments in this discussion, maybe I have my answer, at least partially. A lot of people here suggest to use extensions and other ways to convert webp from the web to… PNG.
And then that PNG gets shared further…
Oh gawd if that’s why so many pngs are on the net… What a way to take a good idea and completely fuck it up. Now instead of a 2MB jpeg or 0.5MB webp we deal with 10MB pngs 🤦♂️
Jamie