There is always some sort of
hardware abstraction in an OS. WASAPI, ASIO, KS and so on are
APIs, they are at software level, to communicate with the driver. None of them "talk to hardware directly".
[1]
Without 3rd party driver, non-exclusive modes:
Audio player/DAW --> Microsoft mixer --> Microsoft driver --> audio hardware
[2]
Without 3rd party driver, WASAPI exclusive mode:
Audio player/DAW --> Microsoft driver --> audio hardware
[3]
With 3rd party driver, using ASIO:
Audio player/DAW --> 3rd party driver --> audio hardware
[4]
With 3rd party driver, not using ASIO:
Audio player/DAW --> Microsoft mixer (potentially) --> 3rd party driver --> audio hardware
[1] and [2] are the so-called "driverless" or "class compliant" mode. Of course, it is not really driverless, it just means the drivers are provided by the OS.
There are several non-exclusive modes:
https://en.wikipedia.org/wiki/Windows_legacy_audio_components
DirectSound (specifically DirectSound3D) used to be "gamers' ASIO" in the Win9x to XP era. In the past Creative cards like Live! (EMU10k1), Audigy (EMU10k2) and X-Fi (CA20k1/2) offer hardware DSP to reduce CPU load and latency via EAX, as well its competitor A3D. However, Windows audio architecture has completely changed since Vista, and caused the downfall of EAX. There is a newer gaming-oriented API called
XAudio2.
There are also other non-exclusive modes including MME and WASAPI shared mode, if the playback software/DAW supports them.
In the case of [3] and [4], I am referring to a dedicated driver, not something like ASIO4all.
In [3], the Windows software mixer is replaced by the driver-controlled hardware (if available) mixer/DSP for lower latency and more features. If you buy an interface for these features, you are supposed to install a driver. ASIO is by no means legacy, obsoleted or for old OSes/software only, it is used to enable the additional features.
As you can see ASIO for my soundcard exposes more I/O channels than other APIs. The additional channels provide flexibility for signal routing and effect processing in the hardware DSP mixer.
Therefore ASIO and DirectSound3D provide hardware acceleration rather than bypass everything for "unpolluted" sound, just like GPUs need a driver for 3D graphics, shader and video codec acceleration. For a simple USB DAC without additional features, there is no need to install a driver solely for ASIO, except for compatibility reasons. Also, remember once you have a 3rd party driver installed, WASAPI (exclusive or not) is subordinate to the 3rd party driver, you should think they are "Creative WASAPI", "RME WASAPI" and so on, they are likely to behave differently than "Microsoft WASAPI". Read the link below:
https://www.audiosciencereview.com/...-difference-in-sound-quality.7029/post-368504