Celebrities aren't born celebrities. You have to grind for years in the fame mines to level up to that point. But there's a reason why it's called "show business" -- if you're in this business, you literally have something to show for it. It might be not their proudest moment, but they can't stop you from re-watching those old movies and shows and going, "Hey! Isn't that...?"
These are no longer just another face in the cast, but their old work still exists as a hopeful reminder that anyone can make it to the top. Yes, even us.