Modern CPUs can ether do or emulate this, probably using less power than a sound card.
Very, very, few people have their PCs connected to an AV receiver or multichannel speakers, but positional audio is still widely supported in Windows applications using Xaudio2.
The reasons sound cards went away is the use cases went away:
1. People who want high quality recording shifted to firewire and later high-speed USB external audio interfaces. No matter how hard you try an external metal box with multiple inputs and outputs will always be better than a PCI/PCIe card inside a PC for recording. Rare use case in the recording world for sound cards.
2. Gamers who want 3d/positional audio either use headphones, find the 5.1 integrated outputs to be adequate, or like me, run a digital audio cable to a surround sound receiver. Rare use case in the gaming world for sound cards.
Dolby Atmos is awesome for positional audio in games but there are multiple less expensive and more accessible methods for surround audio nowadays. Decent positional audio can be experienced using a laptop and headphones-- no sound card required.
https://www.pcgamingwiki.com/wiki/Glossary:Surround_sound
Back in the sound card days you had to squint on the back of the box and ask "is this creative 3d? aureal?" nowadays you just plug in 5.1 to your PC's onboard audio, tell windows you have 5.1, and it works (mostly).