If a flying camera was out in the rain, it would be getting wet too, would it not? Besides, as already stated its a balance issue.
Yeah that's what i meant actually, since there is no flying cam in real life which follows car as fast as car goes there is no reason to push the realism and logic in to it.
I guess it's a choice. If i want more immersion i would use cockpit view with rain droplets on window etc. And a clear screen and no distraction on outer cam to see everything better.