It doesn't take more than one person to talk to a woman.
I often find that going to bars with my buddies to pick up girls is counter productive. They're more likely to screw things up than I am. Plus, you have to build up the courage of not just yourself, but your friend as well to go talk to a group of girls. I have an easier time controlling my own emotions than my friends'. Wingmen are either going to be a crutch, or an excuse to stay in your comfort zone.
I think girls also recognize the confidence that it takes to be out without someone else holding your hand and doing all the leg work.
It is a great feeling being out on your own, completely independent and free. You don't have to deliberate on where you going to go, of if you're going to go over to a group of girls or anything. You don't have to hesitate while you and your friends make a decision about how to approach someone.
And when it's all said and done, when you've brought someone home, the victory is so much sweeter as you now know that you need no one's help to do it time and time again completely at will. The world suddenly becomes your oyster. If you see someone you want, you have the power to go talk to her without any connections or introductions. You, at the very least, have a chance--an open door--and no one there to see you should you fail.