It's more for safety reason. And that being that the drivers are crazy enough on dry roads, wet roads make many of them worse. My cars have all been caught in the rain at one time or another, but I prefer to keep them dry if I can. In fact, I took my '64 Barracuda to a show that started out dry but turned into a heavy rain storm for most of the day. That was the only time I took a first place in class!