We have had a few threads about this, and I have been thinking about it a lot and I have a theory. I was looking at the few friends I have who talk incessantly, largely about themselves, and realised that what they have in common is that they were all neglected as children, as in, no one listened to them, or if they did listen, they didn't "hear" them and respond and engage for various reasons.
So my theroy is that it is a "me me look at me I exist" desperate need for attention as proof of existence.
What do you think?