There's rapidly becoming more and more competitors in this space, as well. OpenAI has a significant first-mover advantage, but I don't know that it is insurmountable, and I doubt investors are confident that it is either. That means they're even less likely to have infinite runway.
So I'm not sure there's personal/moral success at this point in the story for the board to begin with.
Monetary - 3/4ths the board is independent. They are not actually employed by OpenAI. There's nothing to promote them to, and nothing in the charter of the non-profit that would give them payouts.