The television converts the signals to 2.0 signals due to the fact that the television will by default output stereo via the television speakers. We have to take into account the fact that not everyone will have a surround sound system, but those who do will probably have a receiver. So we output the surround sound signal via optical cable for those instances.
It cuts down on the instances of HDMI issues, such as imperfect handshaking (industry standard issues, not just Samsung) as well as give you a direct control of the audio for 5.1 applications as well.
I hope that helps explain why it's set up that way.
I am seriously confused about connections here. I intended to connect my dvd player and cable box to this tv via hdmi and route the optical out to my receiver, since it does not have hdmi. However, the owners manual says that doing it this way will only yield 2 channel audio. ***?!?! What's the point?!?! I was really hoping to take advantage of the better quality hdmi and reduce the number of cables I have hanging everywhere. Is this a shortcoming on all tv's due to compatibility problems, or just on the Samsung PN series? Someone please enlighten me!