I'm browsing some of the steelers PBPs.
Its interesting that if they have the lead late, they will run the football almost every time.  For example, they beat the Bengals 19-14.  They had one drive in the 4th where they got called for holding on a run and it was 1st and 20.  The Steelers just went ahead and ran the ball three more times anyway.  They gained 2, 1, and 3 yards to make it 4th and 14.  Then they punted it back leading only 17-14.   Cowher just sat on the ball up by 3.  Turns out they pinned the Bengals to their 8 on the punt.  The Bengals then committed a penalty in the end zone to make it a safety.
In the Jacksonville game they won 17-16, they had another drive where they ran it repeatedly in the fourth quarter.  Staley for 3, Ben scramble for 19, Staley for 3, Staley for 1, Ben sacked, punt.  Steelers were up 14-13 at the time.  That was some really conservative playcalling and the Jaguars got the ball back and kicked a FG to take the lead on their next drive.  Ben led them down to a game winning FG, however.
The pattern seems to be there.  If the Steelers have any kind of lead in the fourth quarter, wether it is 1 point or 20, Cowher will just shut down the offense and run the football, even if it means punting.  That's not playing to win.  That's what Schottenheimer does.