That's a downside. You can't feel the quality. There is some work you simply need to touch. Good print work will not, for the immediate future, look truly respectable on screen. Crisp images mixed with careful typography suffer.
Great work suffers the most with artifacts that are unavoidable cross-platform.
It's about download time and navigation. Broadband access is still not universally available to very many users. And while images can be compressed with better efficiency today than ever before, compressed files don't sparkle. Moreover, most creatives have carefully and skillfully organized their traditional books in such a way as to let the creative tell a story, from beginning to end, as their book is being viewed. The non-linear aspect of the Internet does not provide the creative with control over his own, personal narrative.