“But to me he was never that.” Bilbo says this to Balin after what I am going to assume was the funeral for Thorin, Fili, and Kili. This line says so much. Bilbo never looked at Thorin as a prince or a king, never looked at him as if he was royalty. He saw someone who was determined and fierce, but someone who was also utterly destroyed and down on himself. Thorin Oakenshield was his friend before anything else. By BotFA he was there not because of a contract but because of friendship. Bilbo Baggins needed Thorin Oakenshield just as much as Thorin needed him. Bilbo didn’t have any friends before Thorin, just acquaintances and people he tolerated. Thorin Oakenshield was his true friend.