I always aspire to the theory the Borg are constantly in the process of "fattening up" the Federation. As in, what one does to an animal before slaughter. During BOBW and FC, there really isn't anything too unique about the Federation's capabilities vs many other species in the galaxy. But keep sending a cube here and there, throw in some time travel, and maybe, just maybe the Federation will develop new skills and technology worthy of armada-sending assimilation down the road.
This was something of a missed opportunity.
To our knowledge, no other species in the galaxy managed to create a non-monetary alliance that spans over 8000 ly's and is comprised of over 150 different species.
In effect, the UFP SHOULD have been FAR more technologically advanced compared to what was shown just from that alone.
This would have been reason enough to show the uniqueness of the Federation and why they were saught out by the Collective.
But then Trek writers just decided to scale it down just to Humanity and Earth.
Why?
Trek shows the Federation where humans are part of a bigger interstellar alliance... so its not just humanity that should be of interest to them. The power of free exchange of ideas, resources, technology and bringing in automation into the mix without the interference of money (and focus on exponetnial developments and returns) could have presented a contrast to the Borg collective that do something similar, but in a violent capacity... and in turn, it could have demonstrated that the Federation is capable of advancing extremely fast even if they don't have 10 000 species in the Federation... but say 66.6 times less.
But, that would have also changed the dynamic of the show and how the writers go about Trek in the first place... it would be enlarged the scope of the universe and story-telling too.... something I don't think Trek writers at the time had the mentality for... so they keep it low key and fairly small scale resulting in a bit of an inadequacy when it comes to Borg reasoning.
I also thought that the Borg were basically 'farming the Federation' and because of their priorities being in the DQ, an interstellar alliance tens of thousands of LY's away was not an immediate priority.
Plus, the Borg don't just assimilate all the time... there are long waiting periods to allow for species to develop some unique defenses or technology.
In effect, the Borg should really just go into hybernation or stop asssimilation for 100 years or so... to allow the galaxy to recover and advance - otherwise, if they so wished, they probably could have assimilated majority of the galaxy by now - there's just no advantage to this as they would lose their source of new technologies, etc. (since we were told they are unable to innovate on its own - which isn't exactly correct because if they are able to assimilate technology from multiple alien species and integrate it into their own and adapt to it, that implies they CAN innovate to a degree).
