When we are a space-faring civilisation, national borders will be irrelevant
Q: WHY exactly are the space launch sites located at places that are energetically inefficient to access the planets?
A: Because humans think that lines on the map, on the surface of the Earth, are more important than the planets.
In a REAL space-faring civilisation, we would launch from wherever was "best", because the destination would be more important than the origin.
You take your boat to a good ramp, with easy access to clean, wide-open water and few waves. Why not take your rocket to the equivalent - an equatorial launch site, and pay a small "ramp fee" to do so.
Anything else is pride, ego, hubris...