Earth's orbit is so empty because when you focus on one show at a time, you focus on just the hero ship and the rest of the Federation doesn't exist.
Oh it's mentioned, but usually, there is no real fleet out there ...
The 'clever' people who did the show conveniently did this same thing.
Even when Voyager was coming home or whenever Earth was on screen ... the Moon was missing.
Ok, I understand the emphasis on the planet, but ignoring stellar bodies and everything else is just plain DUMB.
And begging your pardon but in the 24th century, Earth's orbit should be relatively busy and keeping plenty of defensive systems for one thing along with dozens if not hundreds of drydocks and stations ... with the starbase being the only largest object.
I mean really, even on Enterprise, when the Xindy weapon ship approached Earth in order to destroy it there were NO SF ships.
I mean ... apart from Shran's ship my reaction was: 'what the heck?'
At least the novels have sensibility to describe plenty of stations in Earth's orbit.
And Ds9 (although, the fact that San Francisco HQ was successfully attacked doesn't bode well).
I know most of the fleet was destroyed, but Earth should have prepared for a possible attack at any time (any Fed planet should) because they were at war.
To depict humans as the ones who don't anticipate an attack at all is delusional.