Why can't mute people talk?

Answer 1

Well, sweetheart, mute people can't talk because they have a physical inability to produce speech sounds. It's not that they don't want to chit-chat with you, they just don't have the vocal cords or muscles to make those sweet sounds come out of their mouth. So, be a dear and show some understanding for the silent ones, okay?

Answer 2

Mute people can't talk because they have a deformity of their voice box which doesn't allow them to use it (thus denying them the ability to make sounds people use to talk) or they were injured causing the previous to occur.

Another possibility: whilst the above can be true, it's most often a result of hearing problems, as that means a child can't hear speech in order to learn it. Much has been done to help in this field. Another possibility is brain injury, for instance stroke victims sometimes lose the power of speech.