"[Help] Leaving a gym at 1000 prestige. Why?"

#PokemonGO: I observed at my local gym, that a lot of times it is left at 1000 prestige with a single Pokemon remaining. I just observed that happen in the app (too far to quickly go there right now). I wonder why someone would do that.Background:It is always the same (mystic) player with the same Pokemon which is left in the gym.The gym is mostly filled with several mystic players, sometimes mixed, but mostly the same team.Afaik, there is only one active Valor player in my village who takes the gym from time to time.I am instinct and happy to grab it to get at least 10 coins a day.It's a pretty rural area. Only gym in a few km. The next bigger hub is filled with lvl 10 mystic gyms, having the same players in them, and others.So, is there any tactic in leaving the gym that way? I get it, why people leave a gym grey, but why beat it down to 1k prestige and leave the last player in there?Edit: Thank you all. Makes absolute sense. I hadn't thought about training. via /r/TheSilphRoad http://ift.tt/2ifGT3t