What? Well probably because they believe as you seem to? That you need some man to tell you what words really mean and which ones you can believe. But for those who have the Spirit of truth and can believe evident words...the bible is a very simple book to read and understand with some sincerity and faith. The bible itself says in absolute terms that "you need no man teach you" ...do you believe the bible or some man?
I believe the Bible as it was given, not as any man has determined for himself. We were given the Revelation of God to man, ONCE, Jude 3, not piecemeal with even differing interpretations. He gave ONE, and it has remained unified as He is unified with the Father.
Could you tell me which man has the Spirit, or do all of them have the Spirit and the correct understanding of scripture?
Luther, Calvin, Zwingli, Wesley, some more modern ones, Fox, Campbell, White, Smith, Eddy, Russell, Thomas, Hubbard and many others. There are hundreds if not thousands of denominations all with differing interpretations. Hardly speaks well for your method, and obviously not very easy to understand.
I'll bet you have the Spirit of faith, thus what you interpret is the Truth, infallibly?