Why, hm what about being stubborn and rebellious. Jesus washed the disciples feet, in and as an example, he said, " to be abased, and not arrogant, humble, and not high minded, not prediced. He said more to it, he said you have no part with me in the kingdom, if you don't. More on it, in the New Testament, the greatest shall be the servant. Predice, stands out many times. Christ said, if a well dressed man enters your temple, church, and you seat him up front, while the shabby one, you sit in the back. This is a sin. Sin separates us from God. When DAvid prayed, create in me a clean heart oh God. People ask what is a clean heart. The book of acts, says, it is not easy being a christian. Putting the flesh, and the old nature, of rebellion, and stubbornness, under control. Washing feet, is a physical act. But God see's the heart, and it is the act of being spiritually tamed, and not sowing the wild oats, of the flesh. Any wonder it says, surely the spirt is willing, but the flesh is weak. This is why it says, some things cannot be overcome but with prayer, and FASTING. A decision you make to put your flesh, in subjection, and in control. This is the first step. Another answer to why don't believers, do what it says. LIke peer pressure, and influences. No one is perfect, and at the start of a day, and the end of the day, it could be ending very not good, so we ask for forgiveness, repent, and try again, to stay in the Fruit of the Spirit of Christ.