Because if he did they would tell him the exact same thing you just said.
This is painful, but look at the plain stupid losses he has had. In each one, his gameplan and play calling are the reasons his team lost the game.
FSU in bowl game
MI (2011) The 2010 and 2013 losses were bad, but not as stupid as this one
Eight wins. I could go into a few others that I would say he could have done a better job (OU last year...MI in 2010 and 2013) where putting the entire O on the back of Rees was a mistake.
You take those 8 wins and add them into the total and I'm sure he moves up the list