Here's what I found and you're right ->
http://www.advancedfootballanalytics.com/index.php/home/research/game-strategy/120-4th-down-study
So question is, if it's so statistically favorable to do so, why aren't ANY coaches actually doing so? (The article touches on some reasons). You might respond with "CPJ did that against Clemson!" but 2 things about that are notable:
1. We didn't get the 4th down and Clemson immediately scored, which is the absolute worst-case scenario and fodder for other coaches to point at and say "See? That's damn stupid!"
2. PJ only did that once that I can recall (going for it on 4th and short deep in our own territory in the 1st qtr) so even he wasn't convinced it was the right thing to do.
It's going to take a pretty big culture change at the coaching level for the stats you and the article have cited to become Coaching Norms.
(PS: This discussion is entirely about the "in your own territory" stuff. I agree that in almost every case with the ball on the other side of the 50, you should go for it on 4th and short. A good PK or good defense or sizable lead late in the game affects that decision but that's about it)