They used to have Zephyrhills... loved that water.
Dasani is not spring water. It is regular water, from the local water supply, which is purified using reverse osmosis, and then remineralized to enhance taste. This means that Dasani is utterly consistent, something which is a hallmark of all Coca-Cola products.
It is identical, incidently, to how fresh water is made aboard major cruise ships.
While some spring waters may taste better to some (I loved Zephyrhills), everyone has their own taste, so some folks find certain spring waters objectionable. Using the process used to make Dasani, that variability can be controlled. That makes the most sense for a product intended for the very broadest of audiences.