The main one would be because they don't want to get sued. Licensing HAS stopped groups working on projects, they did on GitS, so LMF took over, they did on Gantz, so W-Dreamers took over etc etc. I don't think I've seen many AonE subbed shows, but from what I heard at the time GitS got licensed, they have a policy of not working on licensed anime. So do other groups.