Goddamn, you gotta challenge every post I make, don't you? I didn't say anything about him talking about his past. Anyway, these flashbacks seem to suggest that Sabo and Ace were at least somewhat comparable of an inspiration as Shanks was to him setting out on his adventure, yet all we heard about up until the Grand Line was Shanks Shanks Shanks.
Also, Luffy doesn't know much about Garp, except that Garp wanted him to be a marine. He didn't know who his dad even was until Garp mentioned Dragon at Water 7.