1. "Why Didn't They Just Use The Eagles In The First Place?"
The Eagles are their own character entirely and they don't take commands off men, elves, dwarves or wizards. They might take their time to get involved but when they do, they do it right. While there is actually a reason for the Eagles not simply flying over Mordor and dropping the ring into the fires of Mount Doom (they were scared, the books openly state), there's also the little point about entertainment and drama. It wouldn't exactly have made a very good trilogy if that had happened, would it?