You can always create a Sitemap using your CPanel's services. I don't currently remember the name of the service. I think it's Attracta.
Personally, I always create a Sitemap for all my online projects.
XenForo doesn't have a sitemap in the core because the devs haven't added one
Since I have read from the staff more than once (which technically do not have a say on the development roadmap) that a sitemap is not needed, I figure if they share that opinion it is not a priority.