If you can’t include an XML site map on your website for some reason will this hurt you with search engines? My unequivocal answer is NO.
Although we do recommend the creation and registering of an XML site map with both Google and Bing (by using their Webmaster Control Panels), to not add one is not a serious blow to your potential organic placement on search engines.
Search engine spiders do not need your created XML site map to spider your website. They will by their very nature spider your home page and then follow the text links in your home page to auto discover the other pages in your website. If your website navigation is not text based or is encapsulated in images or Flash then text links to your key inside sections as well as your own website HTML based site map should be provided on your home page. These links will typically appear in the footer. Doing so insures that you feed search engine spiders a way to travel and discover the pages in your website.
So if you can’t create an XML site map for some reason for your website all is not lost. Just make sure that you have created text links in your home page content that point deep inside your website.