Of the most important on-page SEO factors, the content of each page is obviously important. However, the inclusion of a large number of pages also gives your site a lot of credence in the eyes of Google. This is because Google loves content, and the more of it you have the more weight you will receive. Obviously the quality, relevance, and optimization is important but generally speaking the more content you can provide the better. This content can come in various forms and by optimizing every page you can also target a much greater number of keywords with more effect.