[sborra]

There's much less competition (if any) in rail travel for any given route.

[Symbiote]

There's also no tax on jet fuel.

A high speed train almost always has a lower speed competitor, although it may be run by the same company.

[emteycz]

Definitely not the case in EU and where so, it's only because of governmental inference in the market. Czechia deregulated few years ago and instantly (literally the first day the deregulation came into effect) there was 10+ new rail travel companies operating on basically every conceivable route.