Writing-wise, I honestly get why he's included as a character. If you let the story just be somber and stoic, then a lot of the pages would get reduced down and we don't get to see much of the protagonist's personality aside from maybe her inner-monologue; In which each chapter could just have a rinse and repeat of retrieving the body and delivering it to an ungrateful client. Like yeah he's an annoying character and I do hope he stops himself, or that he could be written to be more meek, but he is providing a lot of spice that opens up how the world works in context of the protagonist. Once he's done that he'll probably mellow out more.