I have friends in the automotive industry, including 2 that work for suppliers of in-vehicle entertainment systems.
The automotive companies isolate entertainment system modules from the rest of the vehicle to minimize legal liability for the operation of modules that are not part of the actual vehicle operation. Basically, they are treated as untrusted. Any vehicle status information gets to the entertainment system via a special gateway module. The information that is relayed is carefully reviewed for potential legal liabilities. The fact that a given signal is required to be available via the OBD port is not sufficient justification for relaying it to the entertainment system.
Even, for example, in vehicles where notification sounds are played through the entertainment system's speakers, the sounds are generated as a secondary function of a vehicle control module and provided to the entertainment system as an audio input. AND the sounds are also emitted by a speaker connected to the module providing the sounds.
Also, in vehicles where "driver information" is presented via the same display used for controlling the entertainment system, the display and it's user controls are part of the Driver Information System, which sends (among other things) commands to the entertainment system and receives (among other things) status from the entertainment system.