There are a couple reasons why some men have deep voices, and others have a higher pitched voice. Vocal pitch depends mainly on the vocal cords known as the larynx. The thicker the larynx is the deeper the pitch.
Your voice box must be calm, and have less stress. If the muscles in your voice box is tight it will only cause your voice to become higher. Think of a guitar string the thin wires produce the highest pitch sound, while the thicker ones produce the deepest. As you add tighten the strings on the guitar the sound becomes higher, and higher.
Breathing patterns also affect your voice, it is proven men who breathe through their chest have a much higher voice than a man who lets their abdomen do the pushing as they breathe.
Diaphragm Breathing - Like most people as crazy as it seems your probably breathing the wrong way. Who can ever figure that people can end up breathing the wrong way.
What I want you to do right now is too stand up. Now take a deep breathe.. After your done I have a quick question okay.. go stand up, and breathe. Did your shoulders & chest rise as you took your breathe? If it did, well you were breathing the wrong way. Breathing through your chest is the improper way of breathing it strains your throat area, and ultimately causes a strain on your own voice.
To breathe the correct way think of your belly moving in, and out. Your chest & shoulders shouldn't even move. Breathing through your diaphragm gives you more power to your voice, will deepen your voice, and cause less strain on your voice.
Posture many people get in the habit of having very bad posture. Without realizing the effect it has on their voice. Maintaining good posture is essential for proper functioning of your vocal cords. Don't you slump your shoulders and push your chin forward, that is the extremely poor posture it restricts your throat and crushes your vocal cords so that less air can vibrate over them to create the resonance needed for a deep voice.
These are the reasons why some male have deeper voices than others; a lot comes down to genetics. However, there is a way to train your voice just like a instrument to the pitch that you would like to produce. Remember just because somebodies voice is high pitched; that does that mean they are stuck with that voice.