Sitemaps demonstrate high-level Information Architecture.
Whilst I have focused less on sitemaps in recent times, due to interactions often being difficult to represent, sitemaps are still very useful tools.
Typically, for content heavy websites or intranets a sitemap will help form the foundation of the high-level navigation structure.
Sitemaps also serve as tools to provide guidance to content/page creators to select the appropriate template design via the client’s content management system.
EXAMPLE:
This examples opposite demonstrates the high-level IA of both a mobile app and an intranet.
The red-orange tags in the lower image denote the required page templates for intranet pages.