No, he is not NECESSARY. Note that word. That means he is not needed. However, it is good to believe in God and life after death. Looking at Christianity and Jewish religions I believe these were created purposely to help people and their lives. People who follow these religions typically have more money, more determination, and better jobs. They get what they want. They do not fear death, they are happy with themselves. They are generally happier.
Yes, there are the annoying ones that we wish we could kill in their sleep. Even so, it is foolish to refuse the facts.