Down by eight within around five minutes left in the game, the Steelers drove down the field an scored with a minute left, then failed to convert for two points. The problem is that on that drive, the Steelers used 2 of their timeouts and left themselves with no alternate strategy other than an unlikely onside kick.
The argument for the Steelers' approach is that why not use up as much time as possible so that if the Steelers tied the game, the Ravens would not have any time to attempt a last second score. The Steelers did just that. By using their timeouts to make sure the plays were properly called and then by running down the play clock, the team made sure that they were going to score and that the Ravens wouldn't be able to do anything once they get the ball back. Also, With one minute left, Pittsburgh would still have enough time to attempt an onside kick if they failed to convert for two points. However, with the percentages not in the favor of the kicking team, that leaves the entire game to be decided by that two-point play with no back up plan.
On the other hand, if the Steelers used a more up-tempo approach without using any timeouts, in the event of a failed two-point conversion and the Ravens recovery of the onside kick, the Steelers would have three timeouts and could possibly get the ball back. This creates an alternative if the Steelers would fail to convert on the two-point conversion (as they did). Instead of placing all of their eggs in one basket, the Steelers would have a much higher percentage of getting the ball back. This offers a back up plan, which could have helped Thursday night.