why do men have very deep voices and women have very light voices?

Answer 1

Testosterone and that is how our Grand Creator made us. The woman is the weaker sex but can pump iron and take hormones, you know? Then she can get as strong or as deep as any man.

I do have to say one thing though, I have met men with extremely high voices and this is a huge turn off to me.

Answer 2

You obviously didn't hear my daughter when she came out of the army. lol. How about, testosterone (male hormone) makes the vocal cords thicker. Just like the lower notes on a guitar are made by the thicker strings.