That way, the massacre of native populations wouldn't look so dramatic and we wouldn't make such a fuss about it. It'd be considered a mild inconvenience at best.
There's a lot of reasons to kill people, for example they spoil the fishing pond you planned to go to once you retire.
There's the classic outsourcing of production. They produce the goods and you pay them in stabbings.
Nature is a wonderful thing, you can use it to justify a specific number of kills !
But in all honesty this isn't really new. Most quests regarding quillboars and centaurs are about killing your pesky neighbors. And if the quest giver is a goblin or an undead, there's a good chance you'll be tasked with organ harvesting or redistribution of resources.
(Characters name are not mine, I just took screens from a variety of walk-through videos)