Why is content so vital to my web site’s search engine ranking?

To put it simply, search engines read content. Content, content, content!
You should always have information that is relevant to your business or service on your web site. Basically, you need to have content that people would search for and actually want to look at and read. However, this doesn’t mean you should have 4,000 pages of just text. Just keep your content short, sweet, but packed with informational goodness.