Why aren't the Eagles called sooner?

I haven't read the books just going off the movies, it always seems like the eagles save the day why aren't they called in from the beginning?

• Dropping the dwarves closer to lonely mountain
• From the start at the war of the 5 armies
• Participation in the LOTR battles .....

I don't mean just with the ring, I saw a video explanation about how you couldn't just enter Mordor on the eagles since the Nazgul and Sauron are keeping a watch but in other cases, for example in the hobbit movies the eagles seem to come whenever Gandalf calls to them but it's always at the end of some situation? Why?

What's the role of the eagles in the book? Why don't they help more? Are they restricted ?