Thanks for all the responses guys. Pretty much echoed what I was already thinking. I know there are plenty of bassists in Austin, I do think it's a blend of the style (prog/alternative rock kind of like Incubus or Coheed, Pink Floyd, etc) not being super popular in town and them being too picky. Shoot, it also may be that people don't think the music is good enough. But they are in a good situation, have a 24/7 rehearsal space, a van for touring, guitarist is an engineer who has access to high quality studios often for free, singer is a graphic designer who can do the webiste, flyers, logos, merch designs, etc., for free. All members are in their late 20's and are easy going and dedicated. To me it seems like an ideal situation for a bassist wanting to do original rock music.
The music you describe might certainly narrow the field, but I suspect they aren't finding someone because they haven't been forced to. The easier road is to coerce you back into the band, so that is what they're doing. No surpise, just human nature. As others have said, help them find a new bassist and do everything you can to get him or her up to speed. In any event, don't feel guilty. This band isn't paying your bills, so just do what's best for you and your family.