I think people are kinda failing to see the point. Its not only to advance the game to a new group of players, yes there are deaf players out there, but its also to develop Alyx's back story.
If you remember, VALVe is huge on having a back story for all but of course Freeman and G-Man.
Think of when you played EP2 and the ending. How did you feel? (to those who beat it). Didn't you feel that remorse and anger all at once? VALVe just wants to deepen Alyx to a new level. I find nothing wrong with that as the HL series itself has a very deep story thats become more wide open with the OB but also has a lot of mystery to it, such as who the G-Man is or what happened to Freeman those 7 years.