There are some people who prefer to talk with strangers about their problems rather than talking to the people who actually know them.
Besides, there are several cases that a stranger could even give a peaceful and accurate advise than your relatives and friends. (Actually I have been in this kind of situation before... A random girl crying then after that moment I never seen her again though I hope she was okay after telling me those problems that have been hurting her that time). In certain times, a stranger is also wanted by several people who wants to have space in life. (though I doubt if it will work in ONLINE like this).