Because the carnal mind is enmity against God: for it is not subject to the law of God, neither indeed can be. Romans 8:7
In a way, teaching, preaching, and "auto-pilot" thinking are easy. You just follow fleshly ideas, and tradition, and never, never depart from human nature. If there is a conflict between what satisfies the ego and the Bible, go for the ego every time. Like a gyroscope, the human mind resists change of direction.
Do I sound like I don't have much respect for human nature? Good, because I don't. Until God intervenes, we are issued with fallen natures. Even when He does, our old natures remain. The Apostle Paul tells of his endless struggle with the old, sin nature. We're born with it, and it remains until we die.
The unsaved only need to deal with one nature, and though troublesome, it gets them by. A non-elect singer or musician can do beautifully. I am not concerned by these things. I have had unsaved friends who did marvelously.
But what I am concerned with--understanding the Bible--shows how our inborn natures are hopelessly marred. A little boy I knew would say, "Lets turn on the lights and see which way the roaches run." The light of the Word shows up our crummy human natures.
This really shows up in doctrine. A doctrine which goes against the human nature of even a pious, otherwise knowledgeable, Christian, brings out the worst in them. If you mention election, for example, you really upset even famous Bible teachers. You have become the enemy of entire denominations.
What peevish, effeminate, little men there are now. Instead of kicking your ass when you are deemed "wrong", and using scripture to demonstrate it, they will turn purple faced, pout, or even cry.
A famous pistol expert (Jeff Cooper) required that any man courting his daughter be good with a handgun. He said, "I still believe a man should have skill in arms." As a Bible man, I believe Christian men should have skill in interpreting the Word of God. Imagine how many men think they are manly because they immerse themselves in sports, but are unfit to defend their wives and children from the wiles of false religion.
It has been said that when two men meet, within fifteen minutes they know who is the superior man. Many times this is based on height or bulk. In which case, a bull would be a "superior man". In a way I indulge in this sizing up, especially with preachers. I think, "Are you diligent in your calling, or have you taken one of the people pleasing, easy ways?"