The Borg assimilate individuals and their entire mind becomes a part of their collective. Every time they to do this, they must gain the exact experiences and legitimate reasonings as to why other lifeforms do NOT want to be a part of the collective.
The Borg must completely understand a individual's perspective, where in any of the Star Trek series, is there an explanation as to why they continue to assimilate and disregard the individual's reasonings? There must be a reason(s) that the collective has that overrides any individuals's feelings/emotions, reasons, and value of free thought.