Nobody really wants to be at an airport. They are located on the outskirts of cities due to noise issues, and you still have to spend quite a lot of time traveling to downtown or even the completely opposite side of the city. It is also extremely difficult to actually build things near the train station due to all the space being required for the airport itself.
Compare the Orlando terminal[0] with a train station like Amsterdam Zuid[1], which is going to be the terminus for high-speed trains in the near future. Orlando has rental cars and taxis. Amsterdam Zuid has 32 semi-local trains per hour, 3 metro lines each serving 6 trains per hour in either direction, 9 bus lines with similar frequencies, and 2 comparable tram lines.
The Orlando terminal is within walking distance of Orlando Airport terminal C. Amsterdam Zuid is within walking distance of a major hospital, a major university, and offices for multinationals like Google, Accenture, and the European Medicine Agency.
When you have to rent a car to get to your destination anyways, why bother taking a train?
[0]: https://www.google.com/maps/place/Brightline+Orlando+Train+S...
[1]: https://www.google.com/maps/place/Amsterdam+Zuid/@52.334522,...