I don't know why he was being kept alive prior to the change in administration. Maybe no one knew how to kill him or the resources couldn't be spent. After the new captains I suspect it's because he'd been fairly non-active and he also used to be a loyal member of their crew.

Compare that to the weight of a bunch of untrained crew you've never been acquainted with and are doing a minimum of work on board your ship.

I know if I were about to lose crew, I'd do what I could to save them. But in his case, it's for the best.