I think some people just want to become freind or get lots of follower and friends' number.But if people who really want to learn language and improve thier language ablity, thay look for exchange partner very hard. I think it is diffrent of each one's goal.

It may be the time difference between countries

May be they are too shy or waiting for your next action.

It may have something to do with the way you approach em; err, I don't know. Don't sweat the small stuff