I use pure Alsa on virtual machines. Image is stripped down so much it barely runs XServer.

Another reason is future proofing. PipeWire is yet another audio protocol, and may not be around in 5 or 10 years.

Not everything has PipeWire. Some flavours of linux has support for 10 years. Even some of my desktop boxes still use Pulseaudio.

And finally what PipeWire actually offers? If you need to dump audio into output, ALSA seems sufficient.