Track speeds and freight companies are the biggest thing keeping us from having night trains between major cities so you can go to sleep at 8 in Chicago and wake up the next morning in Austin, New Orleans or New York
For example, The City of New Orleans comes close to being a Night Train but it runs a full 19 hours, meaning if you leave Chicago at 8 pm, you would still arrive at 3 pm in New Orleans the next day. If the train were sped up to last about 10-14 hours it could easily become a real alternative to flying. Luckily with this example, There should be some infrastructure improvements as grade separation projects happen and the already funded New Orleans to Baton Rouge train increases speeds in that area, as there is a bridge that moves at literally 10 mph over a lake in Louisiana. Nothing to lower speeds by 5 hours but it is a start
