Honestly I think it's because many of the new tower guilds cant build up an enourmous roster because of the absolute jerks who run it. (wont use any names, lol) I have many PMs of leaders who just absolutely bash on other guilds and it really makes the game less enjoyable and more stressful. Just today I had a guild leader come into snow hatshop while we were regrouping and he started talking trash and bashing us calling us noobs...
Guilds like CXE, CoM, Nal, and CJ all have mature leaders (mostly) and you see alot less immaturity that repels players.