I can think of several reasons- although I would submit that many have applied to NWA.

1) Compass is actively hiring and filling class dates.
2) You chances of getting called at Compass are better.
3) Relative seniority at CPS is going to increase a lot quicker than at NWA.
4) A job at CPS right now essentially equates to a job at NWA (via flow).
5) Growth opportunities.
6) Plank ownership.
7) New pilot group that doesn't have the disgruntled feel of NWA's group. (At least not yet).