I know. But it seems like a weird way to do it. I don't think I would walk up to someone who was in the middle of a conversation with someone else and say "wouldn't you rather talk to me instead?" It is a way of being friendly, but it's just odd from my perspective (not that it's wrong).
I agree that it's just people talking to who they feel more comfortable with, but the fact that where I am from more people seemed comfortable talking to the opposite sex and where I am now more people seem comfortable talking to the same sex says something in itself. I assume it has to do with the way people have been brought up to socialise since they were young.
Neither way is right or wrong. However, if you come from a culture where men and women naturally mingle to one where you usually see the men go off in one direction and women in another you are going to find it unusual.
Especially when you are new to another country and you are trying to learn how to behave (like learn how to hold a knife and fork correctly) by imitating the natives. If you are the only one behaving in a certain way (the only woman with a group of men, the only person in the restaurant with the fork in her right hand), you are going to feel strange.
Since I've been here, I've felt "obligated" to go out of my way to make more women friends. My husband has been trying to get me to become friends with his friends' girlfriends and wives since I've been here. They are nice women and we are friendly towards each other, but there just isn't much of a connection.