And from the 6 companies the public railroad was split into, not all are successful: "JR Hokkaido expects to incur a record pretax loss of ¥23.5 billion in the year that ended in March [2017], with the company’s president likening its loss-making business structure — due to loss of passengers caused by falling local populations and the expansion of expressway networks — to “a bucket with holes in the bottom."
https://www.japantimes.co.jp/opinion/2017/04/04/editorials/p...
It's the same with postal services, broadband access and similar infrastructure.
Of course a society as a whole can decide to stop subsidizing these low density areas, but that discussion is largely orthogonal to the privatization topic.
On top of that, railroads (the actual rails and public transport lines) also tend to be a somewhat natural monopoly, so even the high profit lines veer towards minimal service and maximal price.
In Japan right now there are multiple lines that you could take to reach the same destination so there is actually a lot of competition going on.
The most a government can do is figure out beforehand which private company would build and run those cheapest for a certain line, but then you end up with the cheapest solution again, which is not the solution you actually want for infrastructure your economy depends upon.
Also, as the parent pointed out, Japan is a good example for why private companies by themselves aren't enough to run infrastructure like that, since you still need it even if they are unprofitable. And so they need government subsidies. You end up with a company paid for by the tax payer - as if it was nationalized - but with much less control by the government. Basically a money sink that isn't accountable to the tax payer. We have that in Berlin after the public transport was privatized. Can't recommend.
Tokyo is a good counter example: you have metro lines and multiple ground lines, and buses, all competing against each other.
> Japan is a good example for why private companies by themselves aren't enough to run infrastructure like that,
What is your point? Japan is exactly the right example here, you have country-wide private companies operating and running an excellent service (world class) at reasonable cost.
Only a bunch of them are profitable and some are even incurring record losses this year and relying on government money to keep operating.
Can't let them go bankrupt because they're still important. Honestly I explained this in my earlier post, good job cropping that.