Just a thought...
I personally have no issue with taking jumpseaters who don't come to the cockpit or introduce themselves. As long as the gate agents know and our load is ok, it's fine by me. Maybe I am not as power hungry as some

You could even argue that informing the gate agents satisfies the requirement to inform the pic. Just like the PIC is responsible for all aspects of the flight but delegates loading, fuelling, filing flight plans etc, one could argue that the "meeting the jumpseaters" is delegated to the gate agents.
If the gate agent gives me a boarding pass and they tell me there is no need to talk to the captain, why would I do so?