That's probably a complex question to answer, and I won't pretend to be able to answer it fully, but it probably has something to do with the fact that the vast majority of legacy and LCC pilots have turbine experience (usually as a captain) before they get into an A320 or 737. A LCC or legacy pilot will typically have had at least 2 jobs prior to joining the company. They have experience, and little appetite for poor pay and work rules.