They are making a judgment on how long they will be there. It costs training time and resources for a company to just be used for 121 time or simply getting current. The regionals know they're a stepping stone. They just want to minimize the amount of stepping. Sounds insane, but a DUI or a couple checkride fails may help you at the regionals these days. They know the DUI guy or the guy with PRIA issues will have more trouble leaving to the majors than a clean record guy. Crazy times.