Hm, to be the Fall Guy, maybe? Because then failure to defeat the Rangers becomes not-their-fault, it's because of insert-incompetent-general-here. Which doesn't explain why they don't just get rid of them in favour of someone *hopefully* more competent, admittedly, but it's a theory. :)

Or maybe, like in the case of Flurious and Norg, it's just another body around the place so they're not entirely isolated/don't have to do everything themselves.