Talk to most online retailers and they will tell you : "Traffic really is not our problem. Our problem is conversion." And improving Site Search is the first step towards increasing conversion rates. Today's online shopper isn't satisfied with simply browsing through your product catalog - they don't have the time. Research shows that most customers use the Search box rather than browse the product catalog.
As such, online retailers constantly look for good website search infrastructure that can make it easier for their potential customers, once on a site, to find the products they are looking for.