The London to Brighton line has frequent trains. You go to the station, buy a ticket and get on the train. It is not particularly fast but you know exactly how long the journey will take and plan accordingly. Buying a ticket is slow because of the rotten machines, and you may need to get on the train five minutes before it leaves to be sure of a seat, but you just build the necessary extra ten minutes into the journey.
If you get delayed, it is not a problem because there is another train leaving soon.
This is exactly the opposite of the high speed rail concept. Because such trains are very costly to build and run, every seat has to be filled. So passengers end up being confronted with complex fares and find themselves booked into a particular seat on a particular train.
Of course, if they miss their train they have lost their booking and wasted their money. To be certain not to miss their booking, they must allow an hour or more.
High speed rail leads to the paradoxical situation that although the train is faster than an ordinary train, the journey time can be longer! And a frequent service is of little use to the passengers who cannot make use of the potential freedom of choice it gives.
When railways cannot offer an affordable walk-on service, they need to re-think their entire operation. A railway is not an airline and should not be run as if it was.