Because they're the personification of imagery. If they were to speak there would be no reason for them to mime.
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It was supposed to come out in 2006 But it will come out in June 2011 or 2012
Jan. 2010
this means that you wont get what you want unless you speak up
According to the Internet Movie Database (imdb.com) an Untitled Batman Project, starring Christian Bale as Batman, is supposed to come out at some point in 2011.
It's aired on Canada once, but has yet to come on in the USA. She was supposed to be on Sex With Mom and Dad, but it never aired in the US.