It seems to me that a decent number of Impress users want to create pre-recorded online presentations. LibreOffice already has the capability to auto-play voice overs (ie. or any other audio), and it already has the capability to advance slides after a predetermined time.
However, for the ?% of users who want to create a video out of a presentation, the only way to do so is to use a screen recorder. Having to use a separate program is a major pain, and LibreOffice already has everything it needs: why not simply add support for encoding a video format (any format) and then use that encoding to save a playthrough of the slides?
In other words, why can’t I (and many others who use Impress for this same purpose) just go to File => Export and pick AVI or MP4?