Why do you lose your voice when you drink alcohol?

You should not lose your voice with alcohol. If you mean you find it difficult to talk that's a different matter, you have just lost some control over it. Because we use speech constantly and without thought we have forgotten what a very complex task it is. All those sounds and what your teeth, lips, and tongue have to do to form them. There is a lot of damage happening there, that is why it is criminal to drive in that condition.