There are four answers to that: time, money, access to products and services. Managing an entire project takes a lot of time and energy and occurs during business hours. If you work full time, you need a Designer to manage the details and handle problems while you work. Designers get Trade discounts not offered the public, and they pass that discount on to you. In addition, a Designer can help you avoid costly mistakes. We also have access to vastly more products available only to the Trade. Lastly, Designers have relationships with vendors and service pros that speed projects and are beneficial in accomplishing your goals, especially when hiccups arise.