I’d say this is because the concept of a “stare down” is instictive to us primates (or even mammals in general). That is, asserting dominance via staring at others is something we’re born with, and for good reason: our ancestors’ survival hinged on this when being confronted with someone bigger/stronger. That’s why you look down when you’re anxious or ashamed. Canines and felines do the same.
So it’s just natural that people subconsciously transfer this dominance-via-staring to inanimate objects as well, because it comes from a very ancient mammalian instinct.
> That is, asserting dominance via staring at others is something we’re born with, and for good reason: our ancestors’ survival hinged on this when being confronted with someone bigger/stronger.
This explanation is circular. Trying to stare down an enemy who doesn't already care about staring-as-dominance is a losing strategy; they'll just attack you. It doesn't explain how staring-as-dominance came about.
Staring is a precursor to attacks; animals which responded to other animals getting ready to attack them by posturing as if they were ready to counterattack avoided many fights.
Over time, this interaction was offloaded into specialized hardware analyzing gaze -- the one more interested in fighting was the one who stared longer, and that interaction became associated with dominance in social groups.
This was accelerated as the system became more advanced, and more gestures could be recognized as implicit confrontations (and their resolutions).
If you're about to get in a fight, it's important to use the center of your field of vision, because that's the only part that's worth a damn.
For a quadruped, you can see the head, and forelimbs. You get a lot more information from the head.
I was taught, when sparring, to 'loosen' my vision and look a little lower, roughly between the pectoral muscles. But that's bipeds; there's more to track. The stare-down pre-fight behavior was already well-established, and still matters for quadrupeds, many of which are dangerous, so there's been no evolutionary pressure to change it.
So it’s just natural that people subconsciously transfer this dominance-via-staring to inanimate objects as well, because it comes from a very ancient mammalian instinct.