I think it’s debated a lot but from what I remember it’s because the sky is a big empty space, the Eagles are sentient and do what they want, the nazgul patrol the sky and dead kings sense the ring. Sauron has an eye that is ever watching. It would’ve been too dangerous and risky to lose the ring for the Eagles while the enemy still lived.
Why? (I’ve heard but forget)
I think it’s debated a lot but from what I remember it’s because the sky is a big empty space, the Eagles are sentient and do what they want, the nazgul patrol the sky and dead kings sense the ring. Sauron has an eye that is ever watching. It would’ve been too dangerous and risky to lose the ring for the Eagles while the enemy still lived.