The wilderness is no accident on the way to the promised land. Serpents, scorpions, drought: these terrors reveal what a person is made of, because character forms in the place where nothing is given and everything must be earned. A man who has never crossed such ground does not yet know himself.
Water from flint is the point precisely because flint is the last stone you would strike for water. The hardest circumstance can yield exactly what you need, but only after you have been led fully into it. Salvation waits in the desert. You reach the far side by walking through the worst of the crossing.