But there are those who aren't damned good at their job, or even close, and thirst for secondary duties to make up for their shortcomings.
We all knew people like that! One brown nosing chiseller contemporary of mine deliberately chose a secondary duty that he knew was the Stn Cdrs wife's favourite. A kind word from her clearly got him promoted as he wouldn't have achieved it with his primary duty performance. Whereas I got marked down from a spec rec to a rec from the same Stn Cdr because I hadn't chosen any station secondary duties. My time was spent all keeping the Sqn running while my contemporaries were busy running the officer's wives flower arranging club, or some other nonsense. Not that it bothered me as I had a job offer from a well known long haul airline at the time and knew I was leaving.
Also, one thing to remember if you are thinking of re-joining is that these types are now the senior officers of today. I was frequently gobsmacked when I saw which of these became execs in the years since. One of my particularly lacklustre contemporaries who was studying his ATPLs with the rest of us decided that as we were all leaving, he may stay in as he stood a good chance of being promoted. He did quite well in the end. The thought of him being in charge of me is enough to make me think that it's not worth returning.