Why do JWs think that blood transfusions are ungodly?

According to Raymond Franz, it almost didn't p the new doctrine vote at the Watchtower Bible and Tract Society. But the president came in and told the committee to keep arguing about it , but when it hit the printing floor, it became law. How tragic. There are approx 9000 Jehovah's witnesses each year that die for refusing blood. If the life is in the blood, then why not use it to preserve life? God is good.