The critical change which has occurred in photography, photography as an aspect of our society, is the duration of our relationship with a photo. In 1970 a photo was a permanent artifact. We might file it away, but it remained. Our relationship was essentially open ended.
With the advent of digital photography and - far more important - the sharing and social networking ethos, our relationship with most photos is very short. I see an amusing object, snap, edit, send. My relationship with the photo is measured in seconds, maybe a minute. That's a thing I actually do, albeit always as a single recipient transaction. If I shared on a social media platform there might be a secondary life as multiple recipients interact with the photo for a few seconds each. Maybe I would get some likes and the photo would pop up in my consciousness for a few seconds in a day or two. But that's it. The photo lives on as digital detritus, but it is, in the collective consciousness of humanity, gone.
This is new. Photos become far more like the spoken word, the gesture, a live performance. A photo is like a joke or an anecdote told at a party. Photos are ephemera.
A printed photo acquires more weight, more solidity in our consciousness, even today.
This is a reason for books. By placing a photo in a book you render it literally solid. You demand more of your viewer: to see the photo you must touch the book, turn the page. It requires, relative to Facebook or Flickr, infinitely more commitment from the viewer.
This is, really, why I don't share online. Your zero-commitment evaluation of my picture is of literally no value to me. Multiply by the millions more viewers I could reach, and I get a million times zero, still zero, value. I don't care.
I value the judgment of someone willing to lift a book and turn a page. If there's nobody willing to do that, so be it. That won't make me value a worthless +1 a jot more.