When a Hub site is not intended for sharing content, having the search engine and the /search page available can be confusing for end users, as they might attempt to search for non-existent content. This functionality appears to be enabled by default, and there are no options in the Hub site settings to remove these endpoints from the available pages.

A similar situation was reported in this thread: https://community.esri.com/t5/arcgis-hub-questions/disable-the-hub-search-feature-entirely/td-p/1040...