How does poster enjoyment figure? I don't think it's very gratifying when an answer with fewer upvotes than mine is ranked higher, because downvotes are offsetting the difference in upvotes.
They might as well just hide the points. After all, people only post on the site to help others - not to discuss matters like on Hacker News - so biting the hand that feeds you in this way seems self-defeating.
Getting upvoted is a positive experience. Getting downvoted is a negative one. If you don't know that you've been downvoted, you can't get upset about it. It's true that if you go back to a question, look for your relative position, and do the math, you may also have a negative experience, but that's much rarer.
Note that voting isn't the only thing than ranks answers. They also have some subtle reputation system going on.
They might as well just hide the points. After all, people only post on the site to help others - not to discuss matters like on Hacker News - so biting the hand that feeds you in this way seems self-defeating.