Castle was one of the only towers that felt like an actual battle or war. Maybe it is just my opinion, but it felt pretty cool charging through those halls and battling in what felt like the throne room.
It was also one of the only towers that required you to have skill to defend imo (minus the stairs, which were acause of annoyance for many attackers.) It was like a continual guild spar with the large flag room.
I was going to say maybe it's all part of a storyline for the future but yeahhh..To be honest I quite liked Castle alot(Same as liked snow&york) personally would of preferred to stay but hey lets see what comes of it...or doesn't.