PBS did a piece, Frontline IIRC, about regional airlines and airlines like Ryan were discussed.

They essentially underpay employees by A LOT compared with the major airlines. It's how they keep their prices low. Pay little, charge for everything, but discount the price of the regular ticket by a lot.

And WHY would you take that job? Because it gets your foot into the door in the industry.

As a pilot, for you to become a captain (and earn more money), you have to complete certain thousands of hours of flight. And so you want to do that as quickly as possible. Regional airlines are a much easier to be hired into and you can get your routes on a very regular basis to make up all of your hours. Then, when you've completed your hours, you then apply to work for a larger airline with better pay and benefits.