Insurrection: If they asked the immortal aristocrats if they were willing to share the benefits of the whatever particles with billions of people from the federation and they said: "No!" then they would look like egotistic assholes and it would be hard for Picard to defend them... If they answered "Yes" then there wouldn't be any conflict and the movie would be pointless. So the "brilliant' solution found by the writers is that no one ever asks them the question... Sure! That's plausible!

Also, no one among the immortals ever says anything about the problem of either keeping everything to themselves or sharing with others... They just act like that question doesn't exist, even though it's central to the movie!
Congratulations: You've just concocted the most implausible plot point EVER!!!