That seems a little low given just how badly the Seahawks have been losing lately. For the season, the Seahags have an average point differential of -7.1 points per game. Their last home win came in week 13 against Carolina, already owners of the first overall pick in the 2011 draft, and prior to that, they haven't won a home game since beating Arizona in week 7.
Still, the Rams' week 16 performance aside, the team hasn't done much lately to inspire bigger margins from the oddsmakers. All things considered, this is probably generous.