The question may be re-phrased to read

• Where should a space launch site be located?

Just like a car with an IC engine, a spacecraft is really riding a controlled explosion. Therefore it makes sense to reduce the risk at launch - hence, distant from centres of population. A water body such as a sea/ocean is a preference, but there are also space stations located elsewhere E.g. in a desert.

A list of active launch sites is available here For instance, Baikonur & Jiquan are situated in the interior

The question may be re-phrased to read

• Where should a space launch site be located?

Just like a car with an IC engine, a spacecraft is really riding a controlled explosion. Therefore it makes sense to reduce the risk at launch - hence, distant from centres of population. An example of what happens when control is lost may be viewed here A water body such as a sea/ocean is a preference, but there are also space stations located elsewhere E.g. in a desert.

A list of active launch sites is available here For instance, Baikonur & Jiquan are situated in the interior