Lightening is a SERIAL FORMAT with 9pins. So it streams audio and video out in an encoded form.
The AV adapter, need to take that audio and video and turn it into a standardized AV format for the AV plugs.
Now, rather than a lot of odd incompatibilities because Apple added new features to new devices that older docks don't support, we have a common communication format in lightening that should be much more robust going forward.
Apple can add whatever protocols it needs over the serial connection to support future tech, rather than the old way of redefining what some of those 30 pins meant from period to period-- remember the 30 pin connecter started out in a time when there was firewire taking up some of those pins!
People like to ascribe nefarious purposes to Apple or claim apple is "rippng them off" because a small computer that does digital AV conversion costs $30... and they dont' realize that the 30 pin connector didnt' do any conversion of formats was just bringing the signals out to a standard connector. This one actually has to do work, which is why it has a SoC on it.