This is a deliberate part of "precision scheduled railroading" which is neither precision nor scheduled.
Management and investors believe railroads are in long-term decline so capital investments to improve capacity and/or speed are not done. The most important metric is the "operating ratio". If serving a new customer that adds $200m to profit would decrease the ratio by 2% the railroad will not serve the customer.
So as part of this the railroad wants to minimize crew time. On a given section of track with passing sidings the railroad could move more cars by having three train crews going back and forth, creating conists just long enough to fit in the sidings. They could also extend the sidings to allow longer trains.
Instead they reduce to two or even one crew and make longer consists. This often means one crew parks their train and leaves it for an entire day because they won't be able to pass the other train in the opposite direction. The crew has to take a taxi back home and leaves the train idle. Once the other train passes they or another crew comes back and resumes. It now takes 3 days to move the same number of cars it would have taken two before but over those three days the railroad only paid for 1.5 crew days instead of paying 3 crews over two days. Labor costs are reduced, operating ratio looks better, job done.
I'll also point out that US railroad companies hate carrying passengers. They spent decades begging permission to discontinue passenger service, cooking books, refusing to sell tickets, etc so they could discontinue their passenger services. For example what is Caltrain used to run down to LA and was very profitable right up until the day they terminated service.
edit: When management and investors punish railroads for trying to be a better railroad I don't know how you fix that brain damage. We seem stuck in an extremely sub-optimal local maxima.
For sake of argument here are made-up numbers: If you can, by paying some additional labor, with no capex, increase profit by 30% even though operating ratio may slightly decrease while also protecting your business from competitors that is clearly something in the interests of shareholders. If the railroads were run like this I could explain their behavior as standard short-sightedness where they refuse to make the capex investments required to grow their business in the future.
None of this gets into passenger rail service. I don't know that the US market would sustain anything like the numbers railroads did in their heyday but there are absolutely plenty of rail routes that would could have a sustainable and profitable business. With some minor capex they could even do high-speed passenger service to very high profit. Modern 150mph+ train service is stupid cheap and wildly profitable. At that speed you don't have many stops and the travel times are so short your crew labor costs are low. If you already own right-of-way your single most expensive and time-consuming blocker is a non-issue. So far Brightline and CA HSR are seemingly the only ones interested.