Why is that women are usually attracted to the leader of the group?

Me and my bud go out all the time and well.I guess Im alittle better looking (taller,better looking facewise,wide shoulders,Im a dirty blond and people say I look like bradley cooper )but my friend he isnt a bad looking guy and is quite stylish and much better groomed.The only thing is he is unsure of himself and is shy around women and Im not.He even literally tells me Im the alpha male and hes the beta.I try to change him but he says thats his role.Anyways when we are in social settings or when we approach women,they usually go for me.This has happened two times and Im worried if we're in a club that the women will approach me not him and I would be an obstacle to him.The guy doesnt know how to sell himself either he makes more money then me and works near wall st.Do you guys think It will be the same if we go to clubs or social events?