Why Can't You Hear The Audio Like At Authorstream.com?

I've uploaded some of my slideshows at http://www.authorstream.com/ and http://www.slideboom.com/ and the audio is automatically playing while watching the slideshow without the need to download it to hear the audio unlike here at slideshare. Is Slideshare planning to upgrade so that the slide viewer will play the audio as well without having to embed the sound?