PulseAudio supports network streaming, but it's certainly not the main selling point. Important features are:

* Mixing several streams in software, if there's no hardware support (th e FreeBSD sound driver does that as well)

* Dynamic switching between several audio interfaces without stopping the stream, e.g. switching to a Bluetooth headset during a phone call

* Reducing power usage by supporting different latencies for each client application, and then running the hardware with the lowest currently requested latency