You know how some people say C thinks every computer is just a fancier PDP-11 ?

OSS thinks every computer's audio playback devices are just fancier CT Soundblasters.

If you've got a typical generic PC with Intel HDA or AC'97 (or indeed, an actual PCI Soundblaster) and what you'd like to have happen is that you can run your VoIP software, and listen to MP3s and also have new mails go "bing!" then "all the world is a Soundblaster 16" is close enough.

But if you've got a USB headset you plug in to take those VoIP calls, and a pair of bluetooth earbuds for listening to music, but you want new mail noises on speakers - you will start to struggle. These things aren't enough like a Soundblaster, neither in terms of how they're actually working nor in terms of how you expect to use them.

PulseAudio does a much better job there, because it's the right shape, and now it seems PipeWire is a better shape for modern environments where it's not necessarily OK for the software that plays smooth jazz from the Internet to be technically capable of listening in on your video conference calls.

PulseAudio sits above the level of OSS/ALSA to do that magic. Layers are often a good things when it separates concerns and makes the whole easier to handle.