I don't think there are rules that restrict female from joining male teams.
sj67atg6 [#8]why be only girl in an all boy team when u can win in game changers for ez money
joining male team definitely gets more attention.
yoru_instalock [#6]idk bob was in soniqs once and almost qualified
and potter and another female pro was also in EG way back (playing)
Simple answer: Not enough talent. Most of the unsigned female players aren't nearly good enough to play on an academy team (most are asc/imm pug rosters), just like most T2/T3 unsigned male teams, and orgs won't risk picking them up over F/A T1 players. Those who are signed aren't going to leave for a highly risky chance at a higher level of competition, or can't leave because of their contracts. meL specifically was offered a trial with KCP before they left the scene, and that's arguably the best player in all of GC.
TL;DR: doesn't make sense for players or orgs to take a risk when they can get pre-proven T1 talent.