We know too much about how pictures look and should look. And how do you get around making those pictures again and again?
Regularly, people ask me how they can learn more about photography even though they may never have taken an art course. For a while I get enthused about the challenge. I think it would be possible to recommend a carefully selected and sequenced "reading course" that would require the autodidact to find and read (or look at) no more than about 20 books.
What kills the project, every time, is that the books just aren't available. Of the twenty I come up with, only a handful are still in print. Maybe another handful could stand to be substituted for current books without losing too much. But finding a final handful would be dicey even at a big city or large university library.
If I were teaching an actual class, I could procure one copy of the difficult-to-find books and either photocopy the most relevant chapters or have students come in and look at the pictures. But that would only work for a small, localized class (and it can put a lot of wear on valuable, hard-to-replace books). And then I start thinking about individual essays or artists' statements and multimedia sources like videos, and I give up.
One source that's come to my attention lately is this video of Garry Winogrand teaching (there's an alternate site here). It was brought to my attention by O.C. Garza in his excellent essay about his experience as a student of Winogrand's at the University of Texas. (At the link, the .PDF download for the rather lengthy article is just above the pictures.)
Winogrand's importance to the course of photographic history and his influence on American art photography in the second half of the 20th century is difficult to overstate. In some respects it outstrips the important of his pictures. I wish I could also recommend that everybody read Chapters six and seven of Jonathan Green's American Photography: A Critical History along with it. But, naturally, it's out of print. In any event, I suggest you listen carefully to what Winogrand says in this video and try to take it in, even if you're one of those people who aren't convinced by his pictures.