It's the staggering cost of building rails. It takes an extreme amount of money, and it pays off over a long horizon. I don't think there's enough confidence

It's the staggering cost of building rails. It takes an extreme amount of money, and it pays off over a long horizon. I don't think there's enough confidence that trains will retain popularity over that long of a horizon. Climate change regulation might threaten it, another form of transportation might threaten it (i.e. flying, or underground super speedways), or remote work take off and cut demand for travel. Who knows, but I don't think anyone wants to stake billions of dollars on it. Then there's the fact that we've passed a lot of regulations since the last time we built a lot of railways. The environmental ones are a real killer for anything that traverses a lot of terrain, because you'll inevitably end up buried in a sea of lawsuits requiring surveys. The latest high-speed passenger rail I've seen is California's, which is up to an $80 billion budget for ~800 miles of track. I'm sure people will argue it's a bad example, but that's a massive investment, and it won't make returns until it's built. There aren't a lot of people that are willing to put $80 billion on the line in a flailing business sector, where they don't expect to see returns for at least a decade.