Link to book chapter.
It's the urge to share attention above other important considerations that is special about humans. Such a natural tendency clearly gives our species an adaptive advantage.
What justifies that such an urge exists? At the start of a disaster and you're in it, you don't act, you don't prepare when you have the time, you tweet. When danger is clear, we still automatically take the time to just state it, to let others know.
My view is that chimpanzees may or may not be capable of sharing attention, but that's not the most important. What matters is that we do know they're not programmed to initiate it. We are. Because each of our individuals is programmed to direct others to share attention for the sake of it, we as a population emerges far more attentive to interesting details, far quicker to detect significant events, and far superior in terms of the space our collective attention could cover. That we have this urge is clearly useful when you think about humans as a collective.
What good does a strict concept of joint attention do? I think that's to help us find that special about us.
Question: Have we looked at rats?
These are very different questions and should not be confused with each other. They are different questions that need different answers.