That is why, if you feel that somebody, or a group of drivers, is not going fast enough, you go around them on the left, then return to the RH lane when a suitable gap presents itself.
Come on! We did the moon, and reusable space travel. We can figure this out! 
I much prefer being able to pass slow drivers rather than having slow drivers occupying all available lanes.
Happens frequently during rush hour, have drivers “racing” next to each other at 20 MPH below the speed limit.
That’s why I
KEEP RIGHT EXCEPT WHEN OVERTAKING
Or keep right except to pass, as the signs say.
And at this rate, it will still be going on when you return from your next vacation, and the one after that, and the one after that, and the… 
And much of the vacation spent trying to get around the slow drivers camping out in the left lane🤪
They’re not slow, they’re obeying the speed limit.
But you are correct - they should keep right.
Subtopic (instead of creating a separate thread): Why PSL(posted speed limits) Seem So Slow
I’ll start out:
#1. The technology!
Modern cars are built better, accelerate better, better, and for the most part, handle better.
So 55mph today feels like 35mph fifty years ago.
In MD, if you come upon a “rock in the stream” (slow car in the center lane, with traffic passing them on left and right-- it’s invariably either a PA or a VA plate.
50 MPH on a 70 MPH road is slow.
I do 60mph in a 65, and 65 in a 70 zone. Right hand lane.
Ironically, I do 25mph in a 20 zone, because my old 2010 Honda get such good pickup, and is aligned so well it rolls so easy. I match 30 and 40mph posted.
I cannot speak for now, but about 20-years ago, when I was on emergency leave from the military and I was traveling from my home in Virginia to my relatives home in upstate New York, I was stopped 5 or 6 times in Maryland while driving my Virginia plated vehicle (a 1995 Toyota Corolla…).
I was pushing the speed limit but not ridiculously so (under 10 MPH over…), They were interested if I was transporting guns or cigarettes (no guns but a full carton of cigarettes, which one trooper examined)…
I might have been ticketed if I had not shown my Military ID and Leave Papers.
So, if vehicles from the adjoining states of Pennsylvania and Virginia are a bit wary of driving in Maryland, maybe it’s the way some of us have been treated…
Drivers should be wary of driving in Virginia. They upped the speed limit on the interstates to 70 mph but said that going much over the speed limit would result in a large fine. We never go over 75, usually about 70. My cousin was driving to SC from DC on I-77 and was going at least 20 over. She got a fine well in excess of $1000.
States With the Most Speeding Tickets – Virginia is in 7th-Place…
The National Highway Traffic Safety Administration released a variety of statistics about traffic citations, including the number of speeding tickets that each state issues. Surprisingly, Ohio ended up being the state that wrote the most speeding tickets, followed by Pennsylvania. Rounding out the top five were New York, California and Texas, all of which are states that most would expect to have issued the most speeding tickets. Maryland is low on the list due to it relatively small size and fewer highway roads…
Georgia issued the sixth largest number of speeding tickets, followed by Virginia, North Carolina, Massachusetts and Connecticut. Approximately 41 million citizens received speeding tickets, which works out to around one in five drivers. The average cost of a speeding ticket in the United States is $152, although fines and jail time vary greatly between the states.
The average revenue generated through speeding fines amounts to around $300,000 per police officer.
Although I disagree with Chris about the safety and benefits of exceeding the speed limit, I believe it hid right to drive as he describes, anywhere in the country. I have often driven trucks that would not even attain the speed limit and drove as Chris described, in the right hand lane.
When I got bored in retirement I drove a school bus part time. NY Stare law has a 55 mph speed limit on school buses,even on interstates with 65 mph which are usually carrying 75 mph traffic. It felt very unsafe and I was always expecting to get rear ended.
Long double trailers are also limited to 55 mph on the Thruway ( they are not permitted on the other interstates in NY).
When I drove the Thruway Tandems as they are called, I completely ignored the 55 mph limit as did the State Police because we both knew how unsafe a 20 mph speed difference was.Of course the fact that I was paid by the mile with only 2 cents a mile for the second trailer helped make that decision also.
My “right” to drive at or 1-2mph below PSL?
It’s the LAW not to exceed it.
The speed is determined by the drivers as well as other laws. We had a section of road that had four lanes with 55MPH limit, when it was increase to six lanes FDOT dropped the limit to 45 without explanation. Drivers did not tolerate that, state raised the limit.
As far as the LAW, in Florida it was illegal to drive with your four way flashers on, drivers ignored the law, LEOs would not enforce the law, Tallahassee changed the law. I disagree with that change, as I recall, in another thread someone got stopped for not using their four way flashers in a northern state when it was snowing.
To me emergency (four way) flashers are for emergencies, LEOs should investigate the emergency.
Same with drivers camping in the left lane, not enforced, why? I think the fine is too low so LEOs think it is not worth the effort.
A little dissonance here? You purposely overspeed on residential streets and purposely underspeed on freeways?
Only kids in the 20 MPH zone’s.
I’m not reading or replying to all this, I’m just trying to clear out all those red flags. Car related but still this whole conversation should be deleted in favor of checks and debit cards. My humble free opinion only. I charge for better consultations.
My wife spent her high school years to mid 30s in PA-- she said she was always nervous about coming “south of the border” with PA plates. I’ve still got my Mass license (active duty), but have never been hassled. Maybe they expect it of me.