Obviously don't know where the photo was taken, but I drive on a very similar rural backroads. They usually have speed limits of 55-65.There won't be that kind of speed discrepancy on that road in the photo, and on the highway there won't be oncoming traffic and both parties are in cars. The speed discrepancy would be the same on that rural road if the cyclists were a car going 20mph, so no difference.
It's called the Texas courtesy pass and it's happens all the time...in Texas. You'll see a tractor, farm truck or just a regular car and if they see you come up on them, they move over to paved shoulder if safe so you can pass. That being said, you're right, see it less and less with new generation of drivers.I have NEVER had a car pull over for me on a regular two lane road. Drivers just aren't that courteous.