Why do we think anyone knows? Obi-Wan can probably sense it and maybe Yoda, but they're supposedly living out a very exiled existence out of contact from anyone else. The Emperor used droids to build the Vader armor, so how would anyone make the link back to Anakin?
I agree. Outside of Obi-Wan and Yoda, I don't think anyone necessarily knows who Darth Vader is. And unless they told Bail and the droids (why would they?), then I don't think anyone else knows.
Granted, I haven't read many of the EU books, so there might be something else I'm missing.
Ultimately I don't think it matters to 99.99% of the characters as all they need to know is that The Emperor has a new bad-ass enforcer. Nobody really needs to know where he came from and what his pod-race records are.
I think Ashoka is about the only main character that has any real ties to Anakin. So if there is a reveal of Vader's origins, I don't think it would really matter to anyone but her.