Would you please elaborate what you mean by this?
I am familiar with how conversations work or at least how they used to...
This looking at your phone and tuning out of a conversation seems to be somethin new and lacking as you said, manners.
I find demanding someone's attention more rude than not giving attention that's requested. Someone's attention is theirs to give, not something for others to demand.
As for how conversations used to work... When people were boring or uninteresting people would zone out and just uh-hu away. Just smile and nod. It may give the other the illusion that they're not being ignored, but they are.
I agree no one wants to listen to someone drone on and on, or brag about themselves but that is not what was going on in this specific case.
The truth is it was only a lunch and now that I know how going to lunch with these guys works, I just wont bother inviting them again. I just needed to vent a bit I suppose, and you are correct it would be rude to make my opinion of their conduct known to them and would have come across as a demand for their attention.
It's just that I see the sentiment repeated online rather a lot, while whenever I see the situation crop up offline, it's usually someone zoning out of an uninteresting conversation. I felt that observation and viewpoint needed some representation online.