Adding Ambient SFX to the game based off of certain conditions would make terrain exploration much more lively, entertaining, and immersive.
Imagine driving by a beach, and you hear the wind, leaves rustling, and waves as you go, it could activate if you're near a body of water, and the ambient wind sound (separate from your speed wind sound) depends on the weather (if that'll ever be implemented).
Imagine driving by the in the night and you hear night bugs. And during the break of dawn, you can hear chickens. This would be so cool!