Not sure about this specific case, but I suspect at least some of these readers might do it for consistency with e-paper devices, where no scrolling is an hardw

Not sure about this specific case, but I suspect at least some of these readers might do it for consistency with e-paper devices, where no scrolling is an hardware limitation (very low refresh rates, weak processor, battery savings). So it seems to be a bad idea to try to have a one-size fits all standard : we're much better off with two digital document standards : one with full multimedia and interactive capabilities (short of networking), and another, a subset of the previous with the limitations like : monochrome, no multimedia, interactivity mostly limited to (still in-document) hyperlinks... And guess what, we already have two formats that are almost there ! HTML (see also MHTML=EML) and EPUB. (And of course a 3rd one for physical archival and the rare digital fixed layout documents, for which PDF/A already seems to be decent enough.)