It is 180 miles from my home to Portland Oregon. It takes me 2.5-3 hours depending on traffic. Now if I was to drive to say Tacoma, that takes 45 minutes, go to a high speed rail parking lot and park. Wait for the train. There goes 1.5 hours for the theoretical High speed rail. At that point I am 1.5 hours from Portland. Drive or get on a train? I keep driving..... It will be the same with the LA to LV trip.
The people in charge are in on the grift PLUS they are psychologically messed up.
The major difference is all the cities you mentioned are not Las Vegas which tourists by the millions go to each and from LA you have cross a desert to get there, throw in an entertainment car with alcohol, gambling and live TV, if the price is reasonable compared to flying and the schedule is decent it could easily work