Later, at Water 7, Garp was the one who explained to us what Shanks’ really was, and how strong he was! Despite all that, Shanks has already played a very important role in Luffy’s journey towards becoming the Pirate King. He was the one who inspired Luffy to become a Pirate. That’s not all. He also saved Luffy’s life at East Blue, and in that process, he ended up losing an arm.
Shanks has been established as a very important character to the story of One Piece, but that wasn’t always the case. When Oda drew him at first, his editor didn’t think Shanks was interesting enough. Shanks gave a boring vibe, and the story just didn’t seem as appealing to him. This played on Oda’s mind, and thus he decided to make some changes.
Initially, Oda had no intention that Shanks lost his arm, but after an editor told him that the story was not interesting enough, Oda decided to cut his arm off. That’s right! Everyone’s favourite Red Haired Pirate lost an arm because the story wasn’t interesting enough at that point.
What the editor was actually trying to establish was that while the start to One Piece was decent, there needed to be an impact. Oda couldn’t think of anything better than Shanks making a sacrifice, which is often the case in the world of Anime. When you look at Naruto, they did the same thing with Iruka, who laid his life on the line to save Naruto.
So, Shanks’ arm was used as a way to get fans hooked on One Piece. Because of that particular scene, I think many characters began to like Shanks, and the series as a whole. One Piece would’ve been a lot different if Shanks hadn’t done what he did.