There are a lot of factors that have gone into the lack of sales for the Wild Card game.
First of all, I think about 90% of the state of Wisconsin thought that the Packers would
not make the playoffs this year, thanks to Aaron Rodgers being hurt. This was somewhat of a surprise. People made other plans, and thus there aren't as many people who can get off on short notice, right after the holidays, to attend a football game (even if it IS the Packers).
Secondly, despite my boss's attempt to put a happy face on it, the economy in this state sucks. And, thanks to his decision to not participate in Obamacare, there are still a lot of people who don't have economic certainty for 2014. This also ties in to the first reason, as people really can't afford to take a weekend date off from work. And people sure as heck can't afford a $150 single ticket - not after the money they've spent on the holidays.
Thirdly.... well, there's
this. Yeah, you saw that right: -5°F, with temps slated to drop down to -20 (which is cold even by our standards up here).
It's a perfect storm of reasons not to attend a game.