The two edged sword of the seniority system. The employers love it, it deters their more experienced and valuable crew from jumping ship for better conditions. Thus allowing them “squeeze” their crew just that teeny bit more.
With the perennial oversupply of pilots, the seniority system was good for crews - it prevented the dog eat dog scenarios that exist in competitive workplaces.
As flawed as the seniority system may be, the alternatives are far worse.