Why isn't this a rain garden instead of a raised garden?

Please click on IMAGE to ENLARGE view of a raised island flower garden with rain water standing around it. There are thousands of such expensive, wasteful "unsustainable" put-and-take flower gardens in Northwest Arkansas. City planning regulations should FORBID such abominations.

A raingarden in the same spot would be created BEFORE the lot was covered with red dirt for paving, using the natural soil found in all the former prairie areas such as along Fayetteville's Martin Luther King Boulevard. Paving would be sloped to allow water to flow into these gardens instead of into storm drains. This would allow these original-soil patches to harbor native species of grass and wildflowers that would NEVER require watering. The excess water could soak through to the natural aquifer and be cleansed by the soil and plants. In dry periods, the plants would become dormant but revive when moisture returns. Landscape architects and planners know how to do these things. Why are they not required by law?
Someone might suggest that cars would drive into the ground-level or depressed garden spots. But a simple barrier a few inches off the ground instead of a concrete curb would prevent this and would not cost any more than a curb.