You have better visibility on your left side since that is the drivers side (in the US). People passing on your right are a bit harder to see. Also, on/off ramps are typically on the right so that is where the slower traffic will be. By passing people in this lane, you risk traffic disruption.
Don't I also risk traffic disruption by moving into that lane to allow a driver behind me to get in front of me?
Why would the slower driver want to get back in the left lane? That's the point. The left lane is NOT the "cruising lane". It's the PASSING lane. If you're a slower driver, by definition you don't really belong (safely) in the left lane.
The slower driver (me) would want to get into the left lane because if I want to do 75 and the drivers in the middle lane are doing 65 & 60 in the right, I would be constantly passing everyone.
I've only driven on Long Island and from what I've seen the left lane isn't solely used for passing. It's pretty much a faster cruising lane on 3-lane highways. If I'm keeping up with the vast majority of traffic in the left lane then I do belong in that lane. It doesn't happen often but if someone behind me wants to go faster then they pass me by going into the middle lane. I've only had someone flash their lights once and that was well over 10 years ago.
Edit: Sorry guys. I'm not trying to be an argumentative Douche.
Well, you're right about "Long Island"; it's that way here, too, in Connecticut. The point is, though, is that most of them are wrong. They sit there, passively driving, thinking it's their right to do so. That the roads are the way they are doesn't mean they can't all be a SHIT TON better. Start with the fools that sit in the MIDDLE lane at 55 thinking THAT'S their right. Next time you're on the highway, count how many times traffic is bottle-necking around the car in the middle lane just doing it's own thing, oblivious to everything around them.
Speed is irrelevant. If your middle lane is going 65, and you want to go 75, and there's a line that wants to go 80, well, choices have to be made, and in that case, was I you, I WOULD be "constantly passing" the 65 mph cars. They get to travel their speed, I get to travel mine, and the 80's get to travel theirs. Everyone wins. Is it more work for me? Yeah, but this isn't a passive activity.
When you're hurtling a 4,000 pound densely packed mass of metal down a concrete/asphalt plane at 60 miles an hour, there is nothing passive about it. You're there to drive. Not eat McDonald's, or listen to "The Astonishing", or text your girlfriend behind your wife's back. You're there to DRIVE. And if you've got lane to your right, MOVE THE FUCK OVER. It's the law. Literally, you could take an average stretch of highway (more than two lanes, that is) and move EVERYONE over one lane to the right, not one of those cars' travel time or quality would change one iota, and you'd open up an entire lane for faster traffic. You'd have less road rage, less congestion, and less disruption of the flow of traffic.
(And no, this isn't all just me spewing opinions; I was a civil engineer in college who had a couple classes on this, and there's an excellent book called "Traffic!" that talks about this in depth. Some is my opinion in terms of what is right, but a lot is based on science.)