Why didn't Coleman have 25 carries vs. WSU?

Here are some reasons:

1. Many coaches value abstract things like balance, getting everyone involved, formations, etc over doing what works. They won't run the ball if it means ruining the abstract thing they value.
2. There is no glory in calling basic running plays when they are working. Any moron can do it. Sark gets the happy endings from color commentators because of his perceived genius in formations and innovative plays. Many coaches value this more than anything else.
3. Some coaches are just not very smart. These coaches are all system coaches, where they just copy someone else without any understanding of why that thing worked for the guy they are copying. These guys are so caught up in their systems, that they can't see the forest through the trees and make the in game adjustments necessary.
4. Most coaches today look at running the ball as a way to set up the passing game, where the real offense happens. Though they may recognize that the running game is working, they also tend to believe that by running the ball they are sacrificing bigger potential offense through passing and call plays accordingly.

All of these are bad reasons, but I think apply to the majority of coaches. I think this can be especially true with a lot of coaches with NFL backgrounds in college. The margins are so small in the NFL that you scheme, play calling, formations, etc matter much more than they do in college. In college, there are usually talent differences that can be exploited that do not exist in the NFL, so you don't need to be as clever. In fact, this attempt at cleverness often backfires because it can confuse your own players. I think we are seeing a lot of this type of thing with the Huskies right now in penalties and incorrect routes.

The Boise St. coach obviously doesn't care about any of that stuff. He just wanted to win, and when he saw a weakness he pounced on it.