Our text matters because it trains readers to not make an absolute system of the effects of faith in those who exercise it. And, unless you've lived under a rock for the last fifty years, that's exactly what much of the church has tended to do in publications and word-faith churches. Untold fortunes have been amassed by people who sell the idea that if faith is exercised in just the right way a divine law of predictable positive results must follow.
The result of this is faith is measured not by its endurance but by its immediate results. Enough faith guarantees certain results. Weak faith or lacking faith will be revealed in continued sickness, poverty, or a host of other evils.
Understand. We should exercise faith. There are precious promises in God's Word. And they're there to encourage prayer and trust and hope. God is a good and responsive God. He loves to reveal Himself faithful in blessing His people. You'll get no argument from me. We should ask and seek and knock in the face of God's promise.
The problem is the creation of an airtight system. The problem is the mistaken system that contradicts much the data of divine revelation. And thats the importance of today's text.