It's hard to make enemies behave realistically because people will quickly catch on their patterns.

Fallout 76 mobs, for example, make use of line of sight harder than other Bethesda games. They won't spawn where the players are looking, and prefer to spawn at their backs to get a free cheap shot and stagger. With enough players looking everywhere, they might be forced to spawn visibly, but near an object they can use as cover. Also, they have a sixth sense that makes them walk towards a cover if you aim your weapon at them from afar while hidden.

It's also notable that a near-death enemy will sometimes flee out of your reach to regen health, and attack you again when it's healthy enough. They will also flee/cover if they're a melee type and you climb where they can't reach you, waiting for you to climb down.

I guess the idea was making them realistic, but sometimes this behavior devolves into hide and seek, which can become frustrating as they can use ridiculous things as cover, like chain link fences, floor grills, or a sapling.

I have enough realism IRL, I prefer games that prioritize entertaining mechanics rather than frustrating realism.