[runjake]

- The content is normally static.

- They render consistently on any mainstream platform, without access to external resources.

- They load, scroll, and zoom relatively quickly on mainstream platforms.

I don't think PDFs are terrible to view on mobile. I think it works out pretty well. I prefer viewing them than the mess that is an HTML page with CSS. Usually whoever authored it ddin't do a good job of making it pinch/zoomable and accessible.