That's not to say that train seats should ever be more expensive than airplane seats at the same time to departure, obviously.
In the Netherlands there are only a handful of international trains which have variable prices; you can just hop in any local, regional express, or intercity train, and the only price variance is the fixed peak hours surcharge; no seat reservations, no demand based pricing.
But yeah, a lot of European rail also still has a fixed-price fare you can buy on the day of departure – although that fare is usually much higher than the (dynamically priced) saver fare, if available. So functionally, it's just a cap of the maximum dynamic rate, at this point.
I wish they’d adopt airline style! A half empty train leaving in thirty minutes should have dirt cheap tickets. Instead it looks like they robotically raise prices on a time-based model.