You've got thirty seconds to sell your work to the well dressed nemesis who's paying you. Handle the next few moments gracefully, and the project will be one you can be proud of. Flub an answer, and you can kiss excellence goodbye. Are you prepared? Can you deliver?
Who decides what's best for a website? Highly skilled professionals who work with the site's users and serve as their advocates? Or schmucks with money? Most often, it's the latter. That's why a web designer's first job is to educate the people who hold the purse strings.