Thanks everyone for your replies.
The Borg's behavior at any given moment is generally driven by the specific needs of the scene/episode/movie's plot rather than by a hard set of rules - generally if they're trying to set an eerie tone you have Borg wandering around ignoring the crew; if they're creating a sense of danger/urgency/action, you have Borg running around attacking our heroes on sight.
And there's nothing wrong with that approach.
I would accept that as an axiom. That is the real-world explanation behind what is happening in the story, and I definitely understood the intended mood
of the scene. But I guess I should have been more clear that I was asking for an in
-universe explanation to help the story make more sense. I figured this was such a generally popular fan-favorite film that the fans would already have every detail rationalized and explained.
You shouldn't try and apply human motivations to the Borg. They are unimaginably vast.
Sure, that sounds
good. But the Borg are fictional characters created by humans, and the story was written by humans to be enjoyed by humans. So I thought the humans at this board might have some insights to the vast unimaginable motivations of the Borg in that scene, and some humans here do. And also remember, as stated in TUC, "Everybody's human."
You may as well ask why the cells in your body aren't interested in boning up on some Shakespeare.
Angels and ministers of grace, defend us.