The ringwraiths and sauron may have been able to stop them and perhaps flying the eagles to mordor would have been closer to delivering the ring on a silver platter.
the eagles themselves are not animals, they are servants of a god. interfering in middle earth isn't their purpose. Only after their destruction of smaug were they sent to the lonely mountain. Only after the destruction of the ring did they appear at mt doom to save Frodo and Sam.
It would ruin the story
The ringwraiths and sauron may have been able to stop them and perhaps flying the eagles to mordor would have been closer to delivering the ring on a silver platter.
the eagles themselves are not animals, they are servants of a god. interfering in middle earth isn't their purpose. Only after their destruction of smaug were they sent to the lonely mountain. Only after the destruction of the ring did they appear at mt doom to save Frodo and Sam.