Nature doesn't "design" anything. Random variations that have survival or reproductive value tend to produce more of their own kind. Hence how nature can standardize on an interesting aberration.
As for the maple seeds, there are many species of tree that produce similar leafy seeds. Some have highly evolved seeds, like the maple, and others have much cruder and less efficient variations of the same thing. In fact, you can find a continuum ranging from the airfoil of the maple to simple drag chutes for dispersal.