10 Star Trek Questions That Always Confused You
1. Why Don't The Borg Just Send A Fleet After Earth?
This is a question that has puzzled some fans almost since the first appearance of the Borg, but perhaps more important since the release of Star Trek: First Contact. If Starfleet is able to repel a single Cube, why not send more than one? The Borg have vast armadas of ships to spare, so what could it hurt?
Quora user John Boomershine has posited that there is a very good reason for this. Federation space, by 2367, was, though ill-defined, somewhere near 11% of the Milky Way Galaxy (though it could be significantly less than this - this represents the amount of the Galaxy explored by the Federation at that time). This does not take into account the Klingon and Romulan Empires in the Beta Quadrant, which technically stand between the Borg and the Federation.
Assuming that Wolf 359 and the battle of Sector 001 represent single head-on attacks by the Borg, Boomershine suggests that smaller ships were constantly nipping away at the Federation. This would go a way toward explaining Picard's line in First Contact:
They invade our space, and we fall back… they assimilate entire worlds, and we fall back
No world has been shown fully assimilated in the Alpha Quadrant as described here, which suggests there are other incursions occurring without being depicted. If this theory is a fact, then the Borg are actually a far more prescient threat to the Alpha Quadrant than the audience truly understood. Why don't they send an armada to destroy Earth? Simply put, they don't need to.