Since Google is only tracking 40 search engines by default, a lot of organic traffic is ending up as referral traffic. Especially if you are dealing with international SEO campaigns, it is important to have data available from country specific search engines. As a world wide e-commerce website you really want to be able to filter your data per country specific engine because there are a lot of differences between them. That will also mean that the value of that traffic will be unique. Enough reasons to configure your Google Analytics tracking code in the right way.