Why every person just wanna chat with the different gender ?!

Because some people just really want to see their problem from the perspective of someone of the opposite sex. Most of the time they are dealing with relationship problems. When a girl has boy trouble, she might want to hear a boy's view of the situation. I do meet a lot of people on here who don't have any gender preference, perhaps you just haven't encountered them yet :)

Sometimes they are just people looking for someone to flirt with. But I think a lot of the time it's just that some people find it easier to relate to specific genders. I mean, there are some things that I struggle with that I might prefer to talk to a girl, other times I think a guy may be easier. It depends. However, I will talk to either, so long as the person is genuine, kind and not talking to me for the wrong reasons, it's fine.

It's more fun.

i prefer women to talk to... im a girl... because i grew up with more men around.

I talk to people from both genders. It's pretty much all the same to me.