Any game is "anyone's game"----witness Miami's defeat of Chicago.
Obviously, the task of the oddsmaker is to set the line so that half of the bet falls on either side. So, the line is a reflection of what the bettors are expected to do, rather than the personal viewpoint of the oddsmaker.
That said, the Steelers have demonstrated little of what got them to last year's Superbowl. The Saints have won 3 of 4 road games, and played well in their lone defeat at Carolina. Take the Saints and the points.