User blog comment:Ichigostop/Isn't Shanks supposed to already know where One Piece is and how to get to Raftel?/@comment-3429916-20110217200754

Probably because Shanks is not interested in a title since he is an infamous skilled pirate and like Whitebeard he does not like "treasure-hunting". About Buggy, I don't really understand why he created a crew and planned to become the Pirate King but I don't think he is after One Piece either because he simply was too afraid to ask what One Piece was when Roger found One Piece.