An erroneous train of thought
But anyone with even the most superficial knowledge of history understands that this was never - and it not now - the only reason a national government ever took anything into state ownership. Apart from anything else, the huge range of polities that have done this should be enough for the idea that nationalisation equals left-wing to be laughed out of court. Didn't just about every country in the world have a larger role for the government in the development of their railway networks? Nothing to do with them being more or less 'socialist' and everything to do with them following the lead from the world's first industrial nation.
Building rail networks was obviously essential for servicing the needs of developing capitalist economies.
Can we stop this revisionism? The vast, vast majority of the British railway network was built by private companies—not the state.
The first public railways were built as local rail links operated by small private railway companies. With increasing rapidity, more and more lines were built, often with scant regard for their potential for traffic. The 1840s were by far the biggest decade for railway growth. In 1840, when the decade began, railway lines in Britain were few and scattered, but within ten years a virtually complete network had been laid down, and the vast majority of towns and villages had a rail connection, and sometimes two or three.
What the state did do was to completely and comprehensively fuck up the railway companies, almost from the get-go. The state enforced a maximum price for freight carriage, then it ran the railways in WWI, then forced the railways companies to effectively run services for free during WWII. And then, even after nationalisation, the government continued to screw the network. [Emphasis mine.]
Traffic on the railways remained fairly steady during the 1950s, however the economics of the railway network steadily deteriorated. This was largely due to costs such as labour rising faster than income. Fares and freight charges were repeatedly frozen by the government in an attempt to control inflation and please the electorate.
The Beeching Axe was then instituted and was, by any standards, a massive failure. Beeching assumed that, if unprofitable branch lines were closed, people would simply drive to the next nearest station and use the mainline. They didn't.
The closures failed in their main purpose of trying to restore the railways to profitability, with the promised savings failing to materialise. By closing almost a third of the rail network, Beeching managed to achieve a saving of just £30 million, whilst overall losses were running in excess of £100 million. These losses were mainly because the branch lines acted as feeders to the main lines and this feeder traffic was lost when the branches closed. This in turn meant less traffic and less income for the increasingly vulnerable main lines. The assumption at the time was that car owners would drive to the nearest railhead (which was usually the junction where the closed branch line would otherwise have taken them) and continue their journey onwards by train, but in practice, having once left home in their cars, they used them for the whole journey. The same problem occurred with the movement of goods and freight—without branch lines, the railways lost a great deal of their ability to transport goods 'door to door.' Like the passenger model, it was assumed that lorries would pick up goods, transport them to the nearest railhead, where they would be taken across the country by train, unloaded onto another lorry and taken to their destination. However, the development of the motorway network, the advent of containerisation and the sheer economic costs of having two break-of-bulk points made long-distance road transport a more viable alternative.
At its peak in 1950, British Railway's system was around 21,000 miles (33 800 km) and 6,000 stations. By 1975, the system had shrunk to 12,000 miles (19 300 km) of track and 2,000 stations; it has remained roughly this size thereafter.
To try to pretend that the state was responsbible for building the British rail network is absolutely laughable. In fact, the state was responsible for screwing the rail companies and hindering the growth of rail—when they weren't actively closing vast swathes of it down, that is.