If rail travel were more efficient, it would be cheaper. Which it is not.
"Cheaper" and "most efficient" are not the same thing.
Of course they are when the concept of market demand is considered. It's a matter of economics.
Automobiles and airplanes are far more efficient in supplying what the market demands. The fact that the iron horse may be more efficient in supplying a service that is not in great demand is irrelevant.
There is also a difference between price and cost. The train may have a cheaper price, but a higher cost in time:
LA to Chicago (buying the ticket today to leave today):
Amtrak
Duration: 42 hr, 15 min
$287.00
Southwest Airlines
Duration: 4 hours
$391.00
I don't know about you, but 38 hours of my time is worth more than 96 bucks. And I don't have to buy food on a four hour flight.
Not only that, but SW has eleven flights today, while Amtrak has one!