Why do we need MOOCs when we have books?

Over the past few years I've gotten interested in economics, and this summer I decided to finally go through an introductory econ textbook.  It's a good way to learn.  I go at my own pace, I can re-read the parts I don't understand, and I can do, or not do, as many of the problems at the end of each chapter as I think I will be helpful. Would taking an actual econ 101 course be better?  Maybe, but maybe not.

Learning economics in this way makes me wonder, of course, about school. I think about the high school courses I teach, and I think, as usual, that we should try to have a lot of our students' learning be done through independent reading. But I also think about online college courses--MOOCs, to use the appropriately silly acronym. And I wonder--what's the point of a MOOC, when we already have books?

Of course, you might ask, what's the point of lectures, when we already have books.  Lectures, as the name implies, started before there were printed books: the lecturer read his book/lecture notes, and the students copied down what he said, so that they could read and re-read it later, at their own pace.  After Gutenberg, lectures weren't as important, but they continued for various reasons (people like watching people, there could be personal contact with the lecturer at other times, etc.). But as many college students have noticed, lectures are not a very good way of teaching.  I skipped at least half of my lectures in college, and I did okay; I had the textbook.

So why MOOCs? And why now? 
If watching someone like Michael Sandel is so great, we could already, before the internet, watch him on videotape or film.  Why didn't community colleges in the seventies and eighties just show films, instead of hiring actual professors? Why are MOOCs happening now?

To answer that question would require going into a whole array of cultural shifts, but it's worth pointing out that places like Harvard and MIT are not, I don't think, going to outsource their teaching to virtual professors anytime soon. MOOCs, like so many other "disruptive" educational innovations, are a matter of providing a cheaper and shoddier product to the middle and lower classes, while providing ever more artisanal craftsmanship to the upper classes.