Density follows infrastructure more than infrastructure follows density. Building a station in a place is more likely to spring up new businesses (and residence

Density follows infrastructure more than infrastructure follows density. Building a station in a place is more likely to spring up new businesses (and residences) around it. It's not a guarantee and there are a lot of variables in play, but the same reason train stations wouldn't remain "20 minute drive to get to where you are going" are basically the same reasons on average most Interstate stops aren't "20 minute drive to get to where you are going" either. The density map of the US already resembles the US highway map. Many of the few pockets that don't are explainable with old passenger train maps overlaid on top of that. Just adding passenger train-only routes on top of existing interstate highways, stopping only at existing exits, would go a long way to service a lot of the US population. It would also presumably spur more walkability efforts at a number of those exits if it was also a passenger train stop.