Why are good players killing other scavs on factory?

I just died to a player scav after fighting a player and winning and while I'm looting his stuff, I die to another player scav. Look the guy up, lvl 37 with 5.56 K/D. This guy doesn't need the gear, he doesn't need the loot, if he does then why doesn't he just get his scav rep up like an actually good player? Imagine being this high lvl and still killing other player scavs, how down bad do you have to be? How much mental illness do you have to have? I genuinely will never understand.