The powder is fused onto the product, it as excellent scratch resistance properties. It also has a pleasing 'smooth' appearance and forms a sealed skin minimizing corrosion risk.
Unlike wet paint, 'over spray' powders can be collected and re-used! When you consider that in any paint spraying system, only around 50% of the paint for powder actually lards on the job, then large savings are clearly possible if the over spray can be re-used.