The why doesn't really bother me. It's basically just a job, a role they play. People's lives change, some leave to be with family. Some get a better deal. Some want to retire. Some get a better offer. Some have an ax to grind. Some think they are irreplaceable and ask for huge increases, and are let go. Some just get tired of the rat race. People in other industries change jobs all the time. I had two "major" jobs. One for 15 years, which I quit because I decided I didn't want to be in the corporate world anymore. The second job, was supposed to be my "fun" job. Lasted 25 years and I quit because it wasn't fun anymore!!!