The alternative is that you're stuck going 10+ mph under the limit because of a left lane hog.

Banning passing on the right only works if keep-right-except-to-pass laws exist and are thoroughly enforced. Most states in the USA don't have keep-right laws, and those that do, it's never enforced, so many people don't even know it's actually the law.

EDIT: US-26 westbound immediately outside downtown Portland is notorious for left lane campers. The limit is 50 mph, but without fail, there's some moron going 40 mph in the left lane. You wanna go slow? Fine, but do it in the right lane where you belong.

It's generally not allowed, but that doesn't stop people just like the speed limit doesn't stop them.

That's the freedom we're talking about when we say "land of the free".