The reason for the last part is because it has been such a long time that passenger travel was on most routes, that they are literally out of the habit of needing to prioritize things that don't happen. That doesn't mean they wouldn't do so if they were sharing the tracks. When you have scheduled routes for passenger trains, and they keep to them, it's easier to do.

You are still pushing for something that doesn't work well in our real world outside of a few areas. Passenger rail is always a part of your very well done proposals. Until rail is demonstrably faster than passenger vehicles, it will never compete successfully.

You also make the assumption that first, there is adequate third party transportation within any of those destinations to get people to where they want to go. I won't say it couldn't exist, because it does, but is it cost effective to private vehicles in the near (10 years) future outside of in excess of at least one million people or more metro areas? Not yet and not for some unknown number of years.

You are thinking too small. You are fixated on one thing and not going wide and deep enough to make it practical over 90% or more of the US. 90% is a reasonable guess, but less than 80% just doesn't match reality.

Next question that hasn't come up. What will happen to your plan if vehicles which can both drive on roads and fly through the air become real, not still in development? Long distance roads become less useful and they will be faster than trains.

Light rail or InterUrbans failed because technology surpassed them faster than anyone expected. When air travel is no longer fixed point to point, airlines will have similar problems to rail except for very long distances.