According to my personal experience, a lot of chinese people are posting on various of websites looking for english native speaker for their english studying. Meanwhile, many foreigners are having trouble in finding a local friend as a survey taken by this site implied.
So why can't these two needs be matched and satisfied in most circumstances? I guess it can be explained with two words, that are Information Asymmetry which is a economic concept. Information Asymmetry means people don't have the same information with each other.
In our case, it means chinese people who want getting to know foreigners have no idea of where to find one, and vice versa.