First, because it seeks to say something spiritual without being itself scripture. While ALL scripture is inspired by God, all theology is not. Not even those with the best of intentions.At some point, men began to try to figure out just how God and the Son of God fit together. How can there be ONE God, yet Jesus is obviously divine. So what gives? Men came to different conclusions. Men argued their points, each claiming that the other did irreparable harm to the truth of scripture. One side claimed that the other side had denigrated the status of Jesus to a creation.The other side claimed that their opponents had denigrated the monotheistic understanding of God. On and on it went. Finally, they all got together and had it out. One side lost.Except they didn't quite lose, for the over the next few years the losing side changed hands several times. First this one was in favor, then that one was in favor.Why is it that humans cannot accept that there may actually be things that we cannot understand about God? We handle that well when it comes to explaining what bad things happen to good people (i.e., we often go with the fact that the ways of God are past human understanding). But when it comes down to just how Father, Son, and Holy Ghost fit together, we claim we have it figured out. And not just figured out, but we KNOW we're right...and they, the other side, are WRONG. Oh, and it will probably send you to hell if you believe the wrong one.If you think that God will send ANYONE to hell for not understanding the trinity, or not accepting it blindly (which is what pretty much every MUST do), then you need to question your concept of God. Yes, we hold to the truth that the Father and Son have existed--and will exist--for all eternity. We also hold that there is one God. But since we cannot explain it with scripture (and, no, you can't--and everyone who studies it knows that you can't), then why would we dare to claim that someone who doesn't see it OUR way (which we cannot prove from scripture) is going to hell?Well, it sells books. Maybe.But most of all, it lets everyone know that the OTHER GUYS are wrong, wrong, wrong. And you should side with us.Simplification? Sure. But it has more than a grain of truth.