The original question is so preposterous in my view, it scarcely warrants an answer.
The question is a fair one
We can have discussions about abolishing the monarchy, about leaving/joining the EU, about Scottish independence or Irish unification and about all sorts of other things that affect the future of the UK, but it's preposterous to discuss the future of heavy rail?
The railways need billions of pounds in subsidy but around 95% of people barely use them, so it doesn't seem unreasonable to occasionally ask the question about what the UK taxpayers are getting for their money (without getting emotional about the straw-man idea of killing tens of millions of people, or trying to balance it out by the economic benefits of purchasing a couple of pints or justifying the subsidy on the grounds that coach seats aren't as comfortable)
Heavy rail does a number of things very well, there's a sweet spot of time/distance where it's cheap/ efficient/ convenient/ popular (and there are enough people travelling between the same two places, or on the same corridor) - you generally wouldn't wait on a train for journeys of under a mile but there aren't a lot of non-London flows of over a hundred miles where there are enough people going between two places to make a service viable (sometimes a service works okay because it's lots of different flows tied together - e.g. there aren't a lot of Portsmouth - Cardiff passengers but a direct service serves a few significant places so there are enough overlapping flows)
If you want railways, you need to be able to justify them to the 95% who don't use them very often (or don't use them at all) - we live in a country that has closed large numbers of libraries/ sports pitches/ hospital wards/ Sure Starts etc - we can't guarantee the lightly used branch lines will carry on being subsidised long term - we need to be able to come up with good reasons (how much more efficient it is to move five hundred people between two cities fifty miles apart compared to putting those people in cars/ buses/ planes)
Look at how BR managed to close stations pretty much every year in their final fifteen years whilst also growing the overall market (nowadays we'd have squeals that "closing Sinfin Central will significantly deplete passengers connecting onto InterCity services through Derby and the long distance trains through Derby rely on passengers changing from the Sinfin branch to keep them viable" - whereas BR realised that you could trim back certain branches whilst keeping the main network viable and growing)
But let's not pretend that it's the best solution for
every market that it currently serves or that heavy rail is sacred - the fact that some people seem so squeamish about giving proper justifications suggests that they know that some lines are a busted flush and are scared of attention being focussed on them...