Why is rain the nemesis of good driving?

It’s been raining today, so inevitably that means that traffic has been, and will continue to be, utter crap.
See, in California, rain on the freeway means that the 90% of us who know how to make reasonable adjustments in our driving are at the mercy of the idiotic remainder, the ten percent who either
- drive bat-outta-hell style (stuff that would be dangerous even under the best of conditions), or
- drive overly cautiously, almost to the point of pavement paranoia.
The second group is comprised of those folks who see a little bit of water on the freeway and immediately drop to 20 MPH regardless of the traffic around (or behind) them, while the first is home to guys like the dick who was weaving in and out of stop and go traffic on the approach to the Bay Bridge this morning. His antics brought him within inches of my rear bumper — no exaggeration. If I was parallel parking, and had a car as close as his behind me, I would have to get out and go look to make sure I wouldn’t hit it.
Could be worse, though: I could still be in Ohio, dealing with the drivers there.
Or, you could also be stuck in traffic in Calexico. You know no decent person with a brain drives down there! Oh, wait…
i’ve been in philly for three days and it’s been raining non-stop since i got here. i haven’t seen an accident yet.