Patrick,
Most of us are taught that surface water should drain off greens in more than one direction, so I seldom build a green where EVERYTHING goes to the back, but I've done a lot of greens where a good portion of the green drains to the back, partly because I'm a big fan of Garden City.
But I concur with Ken B. that they also just aren't very popular.
Beechtree alone has several front-to-back greens -- the third, fifth, sixth, tenth, fifteenth, seventeenth, and eighteenth greens all take 30-70% of the drainage off the back. Of those, only the tenth and fifteenth ever make anyone's list of favorite holes on the course.
On the other hand, Pacific Dunes has no greens which really slope away. All of those green sites are tied into dune features behind them, and it would be pretty difficult to make a slope toward the dune at the back look natural.
I think it's more about the visibility than the playability. For interesting playability, I still think reverse slopes are an important element -- but not many golfers really like them at Oakmont, either.