A wide variety of diseases and injuries can be responsible for the loss of speech including strokes, certain cancers and neuro-generative conditions which can slowly or immediately steal people's voices. Other people find it impossible to speak due to conditions like cerebral palsy which interferes with the control of muscle groups and can leave some people without a voice from birth.
You actually lectured me via this point, thanks. But what i want to ask is, are you going to loose your own voice after donating it to people who already lost theirs via these diseases you mentioned?
thanks for the comment @austinebizzy. I'm not going to lose my voice after I've donated it. I'm fine (as far as i know) and I'l still be able to use it normally. I'm just making a copy of all the sounds that my voice makes so that it can be used in a voice synthesiser. I hope I keep my voice, it's an important part of my life. If I ever do lose it, it's always reassuring to think that I could in theory retrieve it for my own use! thanks to VoiceID