The separation of the classes between the regionals and the majors have created an environment where you are punished if you have too much experience, for what I've been hearing from former colleagues is that the high time guys at the regional level are having a very hard time getting the jobs at the big three.
A Sr. Captain at a regional may need to take a pay cut plus the loss of seniority when going to a major, with no guarantee of success there.
So depending on age, lifestyle, goals, etc., many if not most high timers aren't really serious about moving on anywhere else, and feel they may be better off being a "lifer" at the regional level. Recruiters know this too and may target younger (not as senior) pilots accordingly.