Before the game against the Cowboys, the Steelers were 16 for 21 on two-point conversion attempts since the 2012 season. That kind of success rate is the reason coach Mike Tomlin attempted to go for two when the Steelers scored the first touchdown of the game.
The only problem for the Steelers was after they failed on their first attempt they kept chasing that lost point all game, and it came back to haunt them in the end. They failed on all four of their two-point tries.
When the Steelers went up 12-3 after their second touchdown they went for two again and failed again.