An SEO typically uses these metrics to report on increases in performance in the search results, usually reporting these to their client, shareholders of their company, or their boss. These KPIs are valuable because they can track things like how a site is performing in the search results, its organic reach (or how much of a market share it is gaining in terms of keyword phrases), how many people are viewing the site, how much time people are spending on the site, and other useful metrics.