Well I got an Uber from my office to Union station, as the metro in DC isn’t great. Obviously no need for an Uber in New York as I could get the subway.
Had I flown to Miami I’d still need a taxi to my hotel, just like I did from the train station. I don’t get that argument.
Why not? Maybe a vicious cycle of insufficient demand.
There are three rental car locations close to Copenhagen Central Station. (Not within it, but within the distance you'd walk around an airport terminal.)
Miami station has car rental, I haven't checked any others.
Damned if I know; best guess would be a consequence of (a) in decently busy cities train stations tend to be in dense areas where it's not economical to stick a car rental, where airports tend to have some acreage around them where you can stick a rental lot and (b) small towns only get a few trains a day and fewer non-residents detraining, so it's neither worth keeping a rental office open just for the train station or even considering its location, since the fraction of rentals from the train station is small compared to eg people getting a rental while their car is in the shop.
So you can take a train to New York, or DC, or a number of lesser cities, and not need a car when you arrive.