Rail tracks spend land in small amounts along their length. The terminals are pretty compact and can be largely put underground, so you can arrive to, or depart from, the very busy central areas of e.g. NYC, or London, or Paris, or Tokyo.

Planes do not require land under the flight path, but require colossal lumps of land for airports. These may be harder to allocate near a city, and you have to spend 40-60 minutes to get from an airport to the busy central areas of NYC or London.

This is a tradeoff, like most things in life.