People talk, because humans need to cooperate
, neither stay close to each other, nor be interested in one another's personal life. Is it the purpose? Does anybody wanna meet personally, or do they (only) wanna talk?
Countably, it's really more simpler for a lot of some interest-driven societies (or company customers) to interact online than personally. There're topics interesting for 1 out of 1000 people (dunno where to search for the people in the physical world). On the internet is no need to travel to a physical place, no need to mind the meeting time and Google is willing to search for it instead of you, and, even, search engines are quicker.
You could ask the same question about Twitter, Google Groups, or Facebook Groups (for example).
Someone has found the virtual world useful.