Could it be those companies are not interested in working with a small video game studio? In case they usually work with the much larger actors of the auto industry.

Or maybe they're operating at a level of fidelity much higher than the game needs? If they're working on simulation e.g. for Formula 1, they might be doing full fledged numerical simulation (FEM etc) rather than simplified models for real time games.

I'd be curious to know more though, what else do you know about this?