It’s maths mate. Game devs aim to maximise player enjoyment, correct? When a player takes enjoyment from someone else, they double that enjoyment for themselves.
Say player A randomly kills player B. Player A has 1 enjoyment from being bored with no pvp. Player B has 5 enjoyment as they’re excited to play through the game. When player A kills player B while they’re doing the story, Player B’s immersion breaks and they’re annoyed by losing galleons and having to go back to where they died. They lose 4 enjoyment. But player A gains 5 enjoyment: 4 from the transfer of enjoyment, 1 from their own pleasure of killing.
Let’s take it a step further. Let’s say Player AG waits and pretends to guard player CZ (a step even further, they’re a Hero so they have to pay for the cargo) while they fill their ketch to the brim with cargo. Once player CZ is finished, player AG lets them sail out a while to maximise CZ’s enjoyment (CZ slowly gains enjoyment the farther they sail)
Then, AG strikes, as CZ is just going out of render distance. He sails over with his brig and annihilates her ketch then kills her while spamming “ez”. The enjoyment that CZ had (5) plummets to -2, but AG gains 15 enjoyment, a gigantic increase in the total amount of enjoyment in the world.
From a utilitarian standpoint, griefing is amazing game design.