Its because when something is illogical, these "brains" retort to using some kind of a streched out metaphor which dumbs it down and makes it make sense, to them at least. So they invent the stupidities like treating a team as a Navy-SEAL unit or a sports team or... coming up with something like "player-coach"...

This ain't about sports.

In most sports you've retired by the age of 40 and most coaches are older than that. I would say that's the reason it's common in sports, but that's the exception not the rule