I think we concentrate more on a one to one conversation - in fact I would suggest that reading counts is "listening to a public pronouncement" - something that is in the environment and not specific to us.

I suspect that twitter counts the same. It's something we don't apply much attention to because it does not look like a human being talking to us.

In fact I suspect that a whatsapp that records one human speaking and then plays it back will have a different attention spike than the text based idea

Edit: of course I wrote the above on autopilot.