^ Exactly. If it ain't broke...
PortAudio is cross platform, meaning it works on linux. It's also the default now, because I guess some people had problems with Xaudio2. For me, Xaudio2 works fine, so I continue using that.
For some users (definetly me) Xaudio2 is very crashy. Crashes my game about 10-20 minutes in, so I just stick with portaudio, no issues there.