Why can't NASCAR run in the rain?

[call_me_andrew]

I keep hearing that NASCAR is preapared along with Goodyear to race on a roadcourse in the rain. I could be wrong, but does anybody know what the NASCAR rule book says about that?

Nationwide: Yes
Everything else: No

For a couple of years they discussed racing in the rain, but haven't heard anything about it for a while now. They used to have the teams set up the cars with a windsheild wiper and other things for rain, but they've stopped doing that.

Once more to the photographic evidence.

I've highlighted the windshield wiper mounts with yellow circles.