Many web design professionals tend to forget that not every visitor will enter through the front door. There are millions of site pages that are effectively a dead end. These pages may have content, but absolutely no links to send the visitor back to the home page nor does the page provide a clue as to the purpose and function of the website.
If a site visitor finds a link to your website through a search engine and lands on a page without navigation capabilities it is likely your site will be abandoned as they search for something more complete.
It is important that each page on your website feature a means of determining what your site is for, what you offer and how to get from one place to the next. If you have pages that are dead ends the chances diminish that your site will be as useful to customers as you want it to be.
Many sites are built with a front door mentality. In this scenario the home page is expected to be the landing pad for all visitors. In truth, search engines rank all site pages making it possible for a visitor to come into your site through a page other than the home page. Sure, youre happy they came, but you have to give them a map...