Why don't you allow women into your social group?
well I can't speak for him but, I can imagine it comes down to:
1. you can't get rid of them easily
2. they meet your friends
3. it could seriously mess up your game.
once they're in your circle you're not getting away from them (one time I met a girl, got rejected, didn't care, but my friends had already invited her to hang out with us, and she started dating some guy in the group, so she was around all the time for the rest of senior year, yay for me),
if they meet your friends either the girl may embarrass you or your friends may embarrass you, or possibly both.
messing up your game is situational, but if you paint a certain picture to impress the girl, and your friends don't agree to play along, they may inadvertently mess things up, or worse, they may want to troll you as a joke.
But don't you think that it would be cool to have two to three women who are your friends that have hot friends?
have you ever actually seen this happen?
it would be cool to have ghost rider's motorcycle:
http://static4.comicvine.com/uploads/original/9/94118/1861790-ghost_riders_.jpg
but I wouldn't count on finding it.
With social circles, you got a 50/50 shot.
...what!?! maybe if you're a world champion at something and hang out with an all female fan club
I think that social circles are the best way to get women.
bare in mind that if you fvck up within a social circle the well is poisoned (unless you go for girls in reverse order of popularity within the group), and you have to make new social circles every time your game significantly improves or else you may be held back by a reputation from a time when you weren't as smooth
what this means is that if you hit on every girl in a circle in a short period of time, you'll gain a rep as a player who only wants to smash every girl, and if you strike out with most of them it's even worse as you'll gain a thirsty loser reputation, but if you were beta at any point you'll give yourself a bad rep with the whole group instead of just the girls who were around, etc.
plus the only real way to improve your game is practice, otherwise you'll only have a bunch of untested theories (and the very last place you want to try out untested theories is in your circle of friends)