Oh god, I just finished Acting Lessons for the first time recently so now I can catch up to all these references. It's only been a day and I'm already trying to repress memories of friends suffering diseases, the Wendy's girl, and most especially burning buildings...
Having started in v0.2 I didn't know about the voice acting outside of Jill during the intro. Having decided to extract more of the game's content, it seems the voice files are still there. As
Kukothemadhatter said perhaps it's only temporarily disabled until he's able to get the voice actors to catch up to the latest version or until the game is finished. Or probably it's scrapped due to cost or simply being an unfeasible endeavour.
Here's some examples: