The economic fact that it’s more beneficial to hire a pilot from your competitors instead of one of your suppliers. Every regional CA they hire hurts their feed to a hub, every ULCC FO they hire hurts their biggest competitor. Almost everyone at a ulcc who has submitted an app in the last month has gotten a call, no 121 turbine PIC required. In fact my ULCC right now looks at PIC as a detriment and thinks it makes you more likely to be un trainable or have bad habits. A320 type trumps cl-65 or EMB-175 pic right now. Plus all 3 majors already fly the bus, less chance you’ll fail.