When I'm talking about leaks, I'm not talking about the extra energy required to constantly run vacuum pumps. I'm saying that HSR infrastructure needs inspection and occasional repair, but not nearly to the extent that a vacuum tube based solution would. Any savings made via efficiency are pissed away by having to pay more maintenance crews and material cost to maintain the infrastructure. The tubes are also much less likely to be able to be automatically inspected like rails can be using inspection cars because any train moving through the tube can only inspect the interior walls. Besides, rail already exists across much of the US for use as freight infrastructure. These same rails, if inspected and tested properly, can be used for high speed rail much more immediately than waiting for tubes to be built. Besides all of this, more aerodynamic trains can and have been built, but are not in use in the US. Instead, we send bricks down the rails. The "immense" efficiency gain from 0.5 atmospheres of air pressure is likely significantly less impressive when compared against well designed trains with regards to aerodynamics.

All of this is also completely ignoring how dangerous tunnels are for fires. Even with proper safety precautions, fires in tunnels are exceptionally dangerous. By venting out the smoke that kills people, you increase the intensity of the fire that also kills people.

"vacuum tube doesnt automatically mean conditions on a spacecraft in sci-fi "

Half atmosphere is less pressure difference than normal passenger planes.