I can only assume Santorum, Bachmann and Huntsman didn't try because they never expected to make it to Super Tuesday. Newt was the first candidate to announce and he scrambled at the end because I believe he too never thought he had a chance.
Paul and Mitt ran last time.
Santorum, at least, was reported to be trying to reach 10k signatures and had announced a ‘last push’ for them before the deadline, but fell short. There’s no point in turning in what you’ve collected if it came to less than 10k. I presume Bachmann was in the same situation.