The thing about conversing with someone on the internet is the lack of actual conversation and body language that takes place. These two are essential to getting to know a person. Simple words on an email or chat interface cannot tell you what the person on the other end is really like. For instance, are they goofy, are they weird, are they compulsive liars... You can't really get that online to the degree you can when in person. Plus real time with a person means more communication in quick time so you really find out if you're compatible or not.