The Greeks just had the pettiest pantheon ever. All their best stories are about mortals who were punished in creative ways for dubious transgressions.
Phineas was the guy the harpies were most famous for, erm, harping on. The gods gave him the gift of prophesy. He used it. They got angry at him for that. So they gave him a daily buffet of great food and had the harpies come in every day and take it away.
Were they specifically charged with creatively mocking him? I don’t think so. I made that part up. But they were charged with shitting in the buffet. I left that part out.
My editors hate the poop jokes.