This is not 100% true and the situations that "not near anything" is true for are varied. DFW was located "in the middle of nowhare" ca. halfway between two cit

This is not 100% true and the situations that "not near anything" is true for are varied. DFW was located "in the middle of nowhare" ca. halfway between two cities when it opened. I visited there more in the past than now but "anything" was building up around it when I did go sporadically. LAX is not close to Downtown LA but there are lots of office buildings out there. San Diego's and Pheonix's airports are very close to Downtown. In the case of San Diego it would be difficult to do anything but reuse the existing railways. I suspect if you look around there are a range of airport distances and a range of abilities to get high-speed railways close to city centers, rather than everything setup like Heathrow vs London.