But what makes you think sound cards don't have buffers? They do, plenty of it. You can easily cause any modern OS to have multiple seconds of audio lag by cran

But what makes you think sound cards don't have buffers? They do, plenty of it. You can easily cause any modern OS to have multiple seconds of audio lag by cranking the buffer size. People just generally don't want that from their system which is makes all this somewhat tricky. Of course if you're doing batch processing you hardly care about latency and the problem is trivial except for the fact that if you hit the play button in your post processing software you still expect instant audio output, especially for deciding cut points and whatnot.