Or have private-key encoding. That’s the case for HDMI: No-one can manufacture devices that aren’t approved.

Of course the funny part is, it’s designed so pirates can only send HDMI output to approved screens (=not recording devices), but for backwards comparibility, they has to allow HDMI-to-SVGA adapter with decoding, so the breach is wide open. But you get the intent: HDMI was supposed to bea fully-encrypted standard with only preapproved devices.