I think "Slower traffic keep right" is part of the problem, nobody wants to think of themselves as "slower". The signs should read "Left lane for passing only" or similar.

Also, I pass people on the right all the time, but I blame them for it. :-) If people don't want to be passed on the right, they shouldn't drive on the left. Simple enough.

At least here, the signs say "State law: Left lane for passing only." Slower drivers never enter the left lane, and the right lane is consistently fast and accessible if you're willing to meet the speed requirements of going above the limit a bit.

Passing on right is legal on roads with two or more lanes going in the same direction.

Laws for passing on the left was intended for roads with one lane going in opposite directions.

Driving the speed limit is considered normal speed according to case law. Slow traffic is going 10 on a 25.