smog liver
Without seniority all workers can take their experience and qualifications to another employer who is offering a better package. I have friends in IT, law and accounting. They are frequently poached by other companies offering better deals. With seniority only corporate or contract jobs might offer a better package, other airlines can only offer entry level packages, so year after year we take the pineapple and stay where we are, getting more and more pissed off.