A question as old as the games themselves.
Who are their RIOs? They don't exist. PA purposefully ignores them because things like RIOs are simply outside the scope of the game. And if they aren't needed for the game to function as a game and narrative, then there's no reason to posit them. The only reason the RIO is in the model is because it'd be conspicuous if it weren't.
Is it possible to fly the F-14 effectively with only the pilot? You might maybe be able to fly it, however unsafely, but certainly not into combat. The RIO is the only one who can control the plane's sensors and weapons systems. It's not a trainer, so there was no reason to duplicate any of the controls between the two seats.