Because the Kansas City game is actually relevant to any Texan fan. Seahawks vs. Cardinals is barely even relevant to Cardinals fans, if that. I'd be hard pressed to find a more meaningless match up concerning playoff teams at this point.
Hell, the Seahawks goal at this point is just get no more injuries and get healthy. It isn't like Arizona isn't going to literally destroy us without even trying with the team that will be fielded Sunday anyway. I'm thinking the NFL isn't happy they made such a stupid schedule for the Seahawks but they are pretty damn biased and obvious so who knows?