game wouldn't gain anything from voicing it, tbh i play any 'voiced' games mostly with voices muted, no music, just allowing effects on low volume is quite enough. FET wasn't really designed and written with voices in mind, else they would likely have tried from early versions on.
also there's the constant issue with synch if someone decides to fast through a scene. common downer for anything voiced, barely can be done.. ok there's the 'mute skipping' solution and one could use multiple streams for several scene speeds, but that's not a really good solution to that. sound files would grow huge with no real improvement.
sure i would agree to a bit more variety in the existing SFX, i mean, as example, any slapping sound is the exact same file, so it seems.