What makes Raiders retreat from a fight with me?

Occasionally when I enter combat with a Raider after a few seconds they will verbally express their fear of the situation (sometimes saying something along the lines of "Screw this, keep your stuff!"), turn around, and begin running away.

As I was still interested in the fight I followed them and can only remember instances of them running a few dozen feet before cowering behind an object and then standing back up and shooting me again since I was close. This sort of retreat is rare and typically I wipe out Raiders with ease, so why do they occasionally run from me?

This seems to be a common problem (Thread) (Thread) (Thread), and the consensus from the community is that this is an effect caused by wearing Legendary armor pieces. For some reason, there's a built-in "threat level" for the player that increases if your armor pieces have Legendary properties. I can't find game documentation that verifies this, but it seems to be what the main cause of this problem is. Players anecdotally reported on many threads that when they removed Legendary armor pieces, enemies stopped being afraid of them.

Legendary Armor Effects for reference. See if any of your armor has properties like these.