One thing is clear if you have a poor website navigation structure it wont help search engines find your pages, but your users may not be so impressed!
So why might webmasters consider creating a XML sitemap?
- It could help with search engines figuring out canonical URLs, although a http 301 redirect is often better.
- The last modified date field in the sitemap file will help search engines understand which pages are changing and when, faster than an organic crawl of your website.
- Information about the pages such as priority and change frequency can help search engines understand and target relevant areas of your website.
- They can also help ensure the validity of links and urls in your website as part of the generation process.
Perhaps most significantly with a free XML sitemap generator, why not at least give it a try and measure the results yourself?