Comment 106 for bug 275998

@mabawsa

From what I can see from the diagram below and its related explanations, one reason is that not every application (Skype may be a good example) uses Alsa. Instead, applications use a variety of sound systems. PulseAudio integrates all those systems into one.

http://upload.wikimedia.org/wikipedia/commons/1/14/Pulseaudio-diagram.png