Because the mind does not always reveal the perfect solution immediately. Also, everybody doesn't have a technique for solving problems, specifically, getting correct solutions from the subconscious mind. It is not taught in public schools. They have to buy books on overcoming obstacles, brainstorming or problem solving. Some people don't even know that the knowledge is available. A lot of information about the mind is considered metaphysical or religious. So when a person has no clue on how to solve their problem or how to get free of their trouble, they don't feel happy.