This would happen to the point where it was almost impossible to organise cross border rail connections.

By seperating the track from the train you can make the train companies compete with each other on a (more) equal footing.

Ironically, most of the 'private' train companies now running on UK tracks are actually Dutch, German and French state owned railway companies competing with each other.

Also, you need to bear in mind that European governments benefit from the other governments strictly following this rule because it means their train operators can run trains in those other countries, but are often less keen on doing so themselves. So there's an interesting dynamic where a lot of countries insist that of course they're following the rules, it's all the other European countries that are unfairly bending them to benefit their train operators.