Because they don't believe your MEC is acting in good faith. Take a look at the vote results for this TA. Your MEC voted 5-3, and apparently it was close to not passing at all. That's an indication that your MEC isn't policing your NC, which the NMB does not like. The economy has nothing to do with why you haven't been released. This NMB is itching to release a few carriers to prove that they are willing to do it, unlike the Bush NMB. They're just waiting for the right situation, which is likely to occur soon.