I made a similar comment to this several days ago.
It takes 46 hours to go from Chicago to Seattle by train, and only 30 by car, for a difference of a whopping 16 hours. Even stopping to sleep for the night, you can get there faster driving. If you don’t get a sleeper, it’s decently cheap at like $120. But still, double the time isn’t appealing to most anyone, especially when actually comfortable accommodations for 2 days are wildly more expensive.
I’d love to travel by train, but it’s just too slow to be practical, even if you really don’t have much going on (if you have pets, for example, that extra week for travel can really get cumbersome). If it was equivalent time to driving (or faster would be great) I think you’d see a lot more people adopting it. Even if it doesn’t replace all the air travel, to just have it cut down cross-country driving would be great. Unfortunately that means a huge investment in rail infrastructure, and a lot of time, to bring the network up to speed.