Drupal allows menu tabs on Views pages. Why, and why not on other kinds of content?
This functionality is built into the Drupal menu system but is not exposed as a configurable option through the web interface by Drupal core.  You would normally have to write some code that implements hook_menu to accomplish this.

Views happens to give a user interface for this functionality, so some people will take advantage of that to do things that maybe aren't best done in Views just because it lets them do it without having to touch code.  I should note that Page Manager and Panels also give you configuration that let you do this through the UI and that would be a better way to achieve this if you have pages that aren't naturally Views.