It's very simple, when you nationalize something, it magically becomes cheaper. Because it doesn't have to pay out "profits" to "shareholder". The way this works is that you can always get a politicians to promise whatever to whomever, as long as it will get him reelected. Then it's up the the public company to constantly pursue quick successes (usually in the form of various prestige projects which includes hiring huge swaths of overpaid and unfireable employees) while neglecting long term planning and maintenance. When called out on it, they demand a larger operating budget, which if allocated, goes mostly towards making the allocating politician look good, and which if not, results in cuts to front line services to make the responsible politician look bad. This is called "rent seeking". Because the service is lousy, and the public, while not liking that, also isn't going to deliver the required landslide in an election, nothing happens. This is known as "the reason large public companies too often become bloated ungovernable unreformable monsters".
While we have the OP as a fine example of my point, it might help to provide an example of your own. In developed economies, nationalization has historically occurred when a business that the public relies upon has become literally or effectively bankrupt. Can you think of an example of an inefficient nationalized industry in the UK, the EU, or the USA? And in what way has nationalization contributed to that inefficiency?
In many cases the services that have recently been privatized were never nationalized to begin with - they were public services, like garbage collection or public transport, that have no obvious market competition model to follow.
Your definition of "rent-seeking" is also incorrect. Rent-seeking behaviour is when an economic agent attempts to manipulate public policy for private gain. A government body cannot engage in this behaviour by definition, as it does not take a profit, and is not private. It can fight its corner though - seeking more funding - but then it must spend that money on things like schoolbooks or hospital beds. This is considered a horrifying waste of resources to the private sector, which knows that those funds could better be spent on yachts and hookers.
I wrote a snarky reply to illustrate that your broad and generalizing assertion didn't really hold up.
My use of "rent seeking" is fine, there is other gain to extract than pure monetary profit. One is personal prestige: Being the boss of a big department with a big budget is nice (and well paid, even in the public sector).
An example of a public company, a railway one even, squandering billions on useless prestige projects: Danish State Railways procuring a small run of entirely custom made intercity trains instead of getting something off the shelf. It's a 5 billion DKK project, close to a decade late now. Also, changing governments failed to maintain the signals, so they're utterly rotten, causing delays daily.
