Traditionally, there has been only one way to build a website, and that was to plan and build the entire website in one go and then leave it untouched for a few years until the next redesign. For a while, this worked. But it was often a frustrating process that went past deadlines and over budget. On top of that, the new website was not guaranteed to increase sales and would sometimes even drive business away.
The designers would create mockups of the website and revisions would be passed back and forth. Once a final design was approved, it would then be passed along to the developers who would bring the design to life. This practice created websites that would look great from a design perspective, but not always connect with the users. If the website looks pretty but users struggle to use it, what good is a new website?