Do you have examples of these games which are best on PC but missing multichannel audio support?
PC games supported 3D Audio long before console manufacturers started talking about it.
The frustrating thing is that Microsoft killed DirectSound3D's hardware acceleration support.
But Creative has software (ALchemy) which can translate those calls to OpenAL, and the hardware can be accessed directly in games which use OpenAL.
So it wasn't actually dead, but it seems that most people thought it was and abandoned sound cards en masse.
I keep an X-Fi card in my PC today, because I still play older games with EAX support.
I am frustrated that a recent change in Windows 10 required these old sound devices to have updated drivers, and my Auzen X-Fi (with HDMI audio) no longer works.
The Witcher 3 is better on PC, but there's a bug where it only outputs stereo on most PCs. It's actually the one reason why I stopped playing it on PC. Stereo is awful.
On topic though. I don't see a reason for sound cards really. I plug HDMI into my video card then into my receiver and it sounds great, especially Dolby Atmos.