Which are used to justify expensive non-Advance tickets.

£80 if I have the audacity to go to greater London today without having planned ahead (3 hour journey + tube). And the same cost coming back - off peak of course. £160! Vs £55 in petrol

Travel at quieter times to benefit from cheaper off peak tickets they used to say. Hah.

And with strikes, weather related closures, maintenance closures, etc I end up having to rebook my ticket at the last minute.

I'd say half of the advanced purchased journeys end up costing me more than just booking the train the day of.

Yes! Now we are getting on to the true cost of advanced tickets.

Fines for making mistakes, rebooking fees, rebooking and having to pay a higher fare, lost tickets because sometimes it's just easier to book a new ticket, losing out when unwell etc...

I bet they make a tidy sum from unused advance tickets

(Great Britain specific):

Although worth noting when it's out of your control the railway does have to offer you options. You don't have 100% of the liability.

And if your train is cancelled you're entitled to take the one before/after for example or get a refund

Though they do make this difficult these days

Does it though? Trains are almost empty most of the time.

They drive to remote places for cheap parking. Sometimes all night. The lines often depart from densely populated cities and bring that large capacity to the countryside. You may get thousands of seats for 2-3 customers. In the other direction it is the same. Last miles people are packed like sardines and bring in all of the revenue. If you have 500 seats a 3 euro ticket would at least pay for the trip. 50 cents is better than nothing. Shops at the train station bring in a large part of the money.

There is also a panopticon effect where people behave themselves decently if people are watching.