We do distribute full Bibles as well as New Testaments, such as in hotels, hospitals and prisons. However, when it comes to schools and personal one-on-one distributions, we tend to give out New Testaments with Psalms and Proverbs.
The main reason for this is because our primary goal is to introduce people to Jesus Christ. If we can ask people to read one thing in the entire Bible, it's the stories that revolve around the character of Jesus and who He is. We want them to start there and then explore the whole story, including the Old Testament, as they dig deeper into the Bible.
This is not to minimize the value we place on the Old Testament. The entire Bible is God's Word and is the foundation of what we as Christians stand on. In fact, we believe that the entire Old Testament is looking ahead to the Messiah, who is Jesus, so it's important to read the whole story.