Ever lost your glasses only to be told they are someplace on your body obscured from your view?
(Like on top of your head?)
It happens. People see things that are right up in their face. And that's about it. So, to make it easier to catch people's eye, we put books there, project slides there, and wave funny flags there. Personal perspective, bias, and expectations make some things invisible to the active viewer and that's what is mean by "blind spots."
The worst part about blind spots is that we all have them. Building trust in an organization is important because when it's coming from someone we know we can trust, instead of brushing away well-intentioned feedback, sometimes we can just look: the paper stuck to the heel of your shoe. You know that don't want it there, but only when you're aware of it. A friend who notices something because they're seeing you from a different perspective than you, can tell you about it.
"Thanks friend! -You've got my back."
"And I've got yours. -A friend in need..."
So, working together we can more quickly find errors, oversights, and omissions. We fill in the gaps we missed, and none of us makes a fuss or keeps score all the time. Trusting each other to tell when it really counts makes all the difference in both work effectiveness and efficiency.