In order to be found on the Internet, you need to be indexed in search engines like Google and Yahoo. Part of how Google and Yahoo decide the relevance of your site is based on how often the content is updated.

Even if your content is static, you can add:

Adding content to your site promotes repeat visitors. If visitors come back to your site and the information is stale then the viewers will not come back to you site. This will make it less likely the visitor will use your product repeatedly.