Why wasn’t the Book of Deuteronomy used in the bible?

The book of Deuteronomy is in the Bible . Many religions uses the New Testament and that's why Deuteronomy is left out. The New World Transalation carries the entire bible from Genesis to Revelation.
The reason why the entire bible should be use is mention at 2Timorty 3:16/17 says," All scripture is inspired of God and beneficial for teaching,for reproving, for setting things straight, for disciplining in righteousness, so that the man of God may be fully competent, completely equipped for every good work."
So that was observant of you to notice a book of the Bible was missing. God gave us the entire bible as a manual or book of instructions to get the best out of life. If you have any more questions about the Bible or will like to have a free bible study, please contact me or visit our website at JW. Org.