> But that problem only occurs 3 weeks out of an entire year.

Which is, of course, when you're statistically the most likely to be traveling.

And the fact that a ticket is valid the whole day doesn't help much when your flight is delayed overnight or by a day.

Some people tend to travel precisely when others are not, and might not run into this problem, seems like that might be your case. Other people travel precisely when others are too, and will run into it all the time. As far as China, every hard sleeper I ever took was sold out in advance, zero holidays.

As far as I can tell, you're entirely confirming what I'm saying.