They always were. It seems to be a case of SEGA losing/throwing away the masters, so all we're left with is the sound files from the original Dreamcast release. The only good voice clips we have are those recorded for the Shenmue "movie". A shame, but what can you do.
I'm debating whether to get this on PC because I watched entire playthroughs of both games fairly recently...
Was there any Switch talk at some point? I find it puzzling that it's on everything except Switch, but maybe the game's code is complex enough where making a Switch port would require a lot of time and resources.