Being a TV spy question

[TomDudgeon]

I want to know something
Why when two spies/ncis agents/undercover cops meet up to exchange info, do they sit next to each other, talk and not look at each other?

If I saw people doing that I would think it was odd and suspicious. If they faced each other, had a quick chat and looked like they were exchanging pleasantries I wouldn't think twice about it.

Because neither wants to be the one with their back to the door and wants the same visibility of the environment that the other has? This is a complete guess but it's what I'd do in the situation.