And then when it's face to face, you have people who aren't lingually adept, what then? Take someone who speaks English as a second language. They may not be able to process what's being said in a face to face as fast as the topic is moving, but in an email thread they can take their time to read it all, and compose a response (which may take longer for them due to English being a second language). It's not as simple as either of you make it seem.