Sure, but they do it with big machines that ride down the rails now instead of lining up thousands of men with sledge hammers.
So what? I'd there isn't a machine, you build one.
Large industries like mining and shipping and the military don't just stop because they can't buy a needed item off the shelf because there isn't a market for it. They build stuff all the time.
I worked in a factory for a few years, and can tell you that if industries followed your "can't do" attitude, commerce would stop.
Let’s say you have a problem and the only way to solve it is with a thingamabob. The thingamabob doesn’t exist, so you need to make the first one. Unknown to everyone, the military, the O&G/mining industry, and the rail industries all try to build one at the same time. Do you think they all cost the same? What about the time to design and build them?
The oil and gas people will call up some machinists and engineers the same day. Time is money and they need the problem solved. It doesn’t need to look pretty. I don’t think anyone would disagree that they would be the first with a thingamabob. First one might break, they’d get Bob on a Cessna from the nearest machine shop with a replacement.
The military would have some meetings, which would spawn more meetings, and eventually put out some requests for proposals. They’d review the proposals and ten years later they’d have their thingamabob. No doubt it would be the most expensive.
The rail industry… the modern, passenger rail industry in wealthy western countries? There might be proposals, or designs or prototypes with large amounts of money spent, but I think it is reasonable to say the thingamabob would never actually be built and used. Look at CAHSR or Stuttgart 21 or Turin-Lyon.
That's not a "change gauge for a 100-wagon freight train" scale operation, and it's not "off the shelf" tech, but we're fairly close I think?
I'm not a train guy, but I'm pretty sure the machine that lifts the track up and allows them to swap out the ties is like 95% of what would be needed for a gauge changing machine.
