As time goes on, I put more and more weight into day/night cycles because of it's contribution to immersion. The less things in the game world change, the more it feels like a game and less something I'm getting involved in.
Give me all the super-accurate tyre physics and how track temperature plays into that or whatever, but what's the point if it never changes? It then becomes the same track in the same conditions and there's no requirement to adapt. But race at night or early in the morning, you'll need to work the car's tyres in a little more to get heat in them for traction... you're shifting things up and forcing the player to learn and evolve and think.
You can do that without it needing to be real time. Just have multiple versions of each track with baked lighting for different times of day.
I don't particularly need to see an exaggerated sunset over the course of a 2-3 lap race