Why WebPs and AVIFs?
I use the WebP and AVIF file format when the SVGs (vector graphics for the web) are too complex or numerous to put in a file or web page. PDFs work well because they can access pages without having to load every image in memory at once. This ability combined with their ubiquity and vector graphics capability (resolution independent graphics) made me decide to use them for a long time.
Vector graphics are more editable and suitable to drawings as you can still change the shapes of each individual elment easily. Bitmap (non-vector) formats liker AVIF, WebP, JPG, and PNG are often used for photos but can be used for drawings too.
This is because to turn a photo into a vector graphic would either be very slow on or crash most devices or else would not reproduce it accurately. I have had some success with this but the photos usually look like drawings and require extensive experience to get good results.
Now I am making sure all my PDFs are universally accessible and so cannot get both the universal PDF with quality vector graphics that I have been able to figure out (without getting into the trouble of using Adobe or Microsoft software - long explanation).
Other Graphics Limitations
The big reason I have to resort to such lengths to avoid JPEGs and PNGs are because the nature of my work looks bad in JPEGs and PNGs are too big without spending much time and wear on my computer compressing them. Apple supports WebP and now AVIF across its entire operating systems - you can put them in Photos or see them in Quicklook, for example.
The big reason I am constrained and need vector graphics (like SVG or PDF) or better compression from bitmap formats (like AVIF or WebP) is because to get decent speeds in my part of America I have to use an ISP who has very slow upload speeds.
I can download huge files easily but putting anywhere near the same size online I get cut off 99% through and then have to reload it again from scratch. One of the reasons for this is it is easier to market streaming video to most customers than uploading files to websites.