As I've said for going on 3 years now...less is more with Romo. The offense moves far more efficiently when we limit his pass attempts to less than 36 in a game.
When you do not threaten to run because:
a) You simply refuse to run the ball
b) You are using shotgun all of the time
It limits your ability to effectively throw the ball downfield. You end up throwing a lot of dink-and-dunk pass patterns and the plays become as such that you need a lot of things to go right in order to just complete the pass. You have to have the receivers lined up correctly, the receivers have to read the coverage and be in tune with what the QB sees, you have to get a good snap from the center, the O-Line has to pick up the stunts and blitzes correct, the QB has to make a good throw and the WR has to catch the ball. And you end up having to do all of those things and more often times just to complete a 6-yard pass. A lot of risk for less reward.
Now that we run the ball, even when the run isn't working that well we can get a lot more simplistic coverages and less blitzes and stunts when we do decide to throw the ball. It makes the QB's job easier and makes the receivers job easier. And I've never met an O-Lineman that prefers to pass protect over run block.
YR