Funny I was just wondering the same thing myself. In fact I would say who wouldn't want to know when they have provided someone a correct answer? If anyone is using the forums for exam prep I think that is pretty silly but even if they are a byproduct would be they are helping others out most likely. I don't think people are just lobbing random answers out there. All the responses I receive are genuine and sometimes the discussion alone is enough to help reveal the answer.
I totally expected to be able to click on my little badge and have it give me some sort of detail regarding where the points came from or at least have a notification that would show up in my mailbox similar to a thread response.