it's because the other characters already had voice packs...
How to install:
*Simply go to "[wherever you put the SW folder]/Mods/Voices" and copy everything in the .zip to said folder [and copy everything in the XML file into the Voices XML].
If you only want one character's voice to be changed or want all but one, open the XML file and delete the row of whichever character you want to exclude [make sure you don't leave a blank row behind]. Deleting the folders that contain the voice clips is optional.