The reason they don't just fly all the way there on eagles is pretty obvious to me. Without going on the whole adventure Bilbo would just be the same hobbit that he was at the start and be no where near ready to take on a dragon. He needs to experience the things that he does in order to prepare him for what is ahead. I thought that would have been pretty obvious on a gaming forum. He doesn't take the eagles all the way there because he needs to level up before he can take on the final boss.
Every girl I ever kissed I was thinking of a pro footballer.