Both should be observed everywhere, but aren't. I remember my dad teaching me to drive back in 1964 and telling me to pull over and let folks behind you past, AND the left lane is for passing, cruise in the right lane. But clearly not everyone's dad told them these things.
Here on the Left Coast, only the left lane thing is in the law. Still, lots of folks ignore it and cruise slowly in the left lane, especially when contemplating a left turn (never mind, 50 miles up the road). There are times I wish I was a State Trooper and could pull 'em over and educate them a little.