Interesting. I'd be assuming it's for making audio tweets, but even then it's kind of restricting. Putting voice in front of other people is something people might not still be ready for.
With text/tweets, you can process the text and what it is about at a glance. With video, you have thumbnails and they usually give you a good idea what to expect from that video. With audio, there's nothing. I think people are not ready for that, because audio only is so hard to filter and "consume" without having to listen to it.
Yeah, audio is kind of... obscure, enclosed, linear, hard to scan, browse or preview. It will be very interesting to see what kind of paradigm change is needed to "open" the contents of audio. I wonder if as of today, it is too hard to recognize words in audio and tag accordingly, for example.
There's speech to text. Even if inaccurate, it gives somewhat of a preview that the user can edit.