Probably the different part of country would be my guess. Besides the low COL and good BBQ, Dallas is pretty meh. LAS area at least has some great hiking/outdoor activities- although Atlanta isn’t terrible in that regard.
Actually, Dallas isnt the deal it used to be cost of living wise. The influx of transplants has caused prices to surge. That might be why some new hires would want to leave. LAS and DFW have basically the same cost of living. If location is important to you then its a no-brainer to make the move if you can.
Dont forget that the legacy majors have hired a ton the past five years. Those hired now will see slower progression and be junior for quite a while. United being the exception but it wont be long before the bulk of their hiring boom is over too. Seniority wise and getting to the best schedules is going to be easier and quicker at a LCC that has higher attrition. Its easy to see why someone junior looking at 300 young dispatchers above them for the next thirty years might want to be on a shorter list with more movement.