Does every page of my website really need to be optimized? ?

In a word - yes. Every page of a website can be a potential entry point for visitors. You can't predict which page or pages will be ranked the best for specific keywords. As such, each page must be individually optimized to for optimal ranking. Collectively, all pages of your website reinforce the common "theme" of the site, which also can help boost ranking. Don't assume that your home page is the most important page on your site.