It is not actually illegal to pass people on the right in California, although I don't think it's a good idea generally, particularly big rigs, who have a huge blind spot there. I drive relatively slowly -- of late, I've been sticking to 55 mph to save fuel. So I'm usually in the rightmost through lane ("life in the slow lane"). However, sometimes I'll move over one to the left if the slow lane is even slower than I am or if there is lots of merging traffic or I know that the right lane is going to end or get forced off in a mile or three.
I get passed a lot, on both sides. But there seems to be a particular breed of driver who can't bear to pass on the left under any circumstances. This morning, while driving over the (three lanes each direction) San Mateo Bridge, I was holding to the right lane at 55 mph and another van came barelling up behind me at speed, but then slowed down and stewed behind me. Traffic was pretty light. There was plenty of room for him to pull out and go around me, but he wouldn't do so. Instead, he fumed. As we entered Foster City, I pulled into the middle lane because the right lane becomes part of the exit for US-101, but I continue straight on CA-92 through San Mateo. The moment I did so, the guy behind me floored it and went tearing down the road (passing me on the right) probably going at least twenty mph over the speed limit. (Which did him no good, as there was a backup onto US-101, so he had to jam on the brakes as I went rolling through the interchange.)
What is it that drives (ahem) people to do this? I have a theory that people assume some sort of magical protection against speeding tickets as long as they stay in the slow lane. That is, if in this case the guy had pulled out and passed me, he was subject to a speeding ticket, but as long as he stayed in the magic right lane, he was immune from tickets even though he was driving 70 in a 55 zone.
I wonder if anyone has ever done studies about why drivers act this way, and if so, what they found.