What is the purpose of Master Display in Views module of Drupal 7? Why is it not present in every Drupal 7 installation? I have been using Views on Drupal 7 a lot and I enjoy it every time. Great module. I have always noticed the existence of "Master" display while creating views but, never bothered about its existence until today when I noticed that there is no "Master" display in my another server running the same instance of Drupal 7 (same version of Views and Views UI modules)? The two servers differ only in OS, Apache, MySQ and PHP versions, shown as follow:  


Core      : 7.31 
Views     : 7.x-3.8 
Views UI  : 7.x-3.8
PHP       : 5.3.3 and 5.4.16
Apache    : Apache/2.2.15 and Apache/2.4.6 (CentOS)
Database  : 5.1.73 (MySQL) and 5.5.37-MariaDB
Centos    : 6.5 & 7.0  


I am a bit confused why "Master" display is not present in recent server but, is available in my other server even though both run same instance/version of Drupal 7? I would greatly appreciate if you could share your knowledge/understanding of "Master" display and its existence/use/purpose (in theory or practical examples if you got any).
To always see the Master Display you need to set the 'Always show the master display' setting at 

admin/structure/views/settings


The Master Display is a convenience and time saver when you have a set of related displays (block, page, feed etc.). You create the master view and then all of the other displays are 'clones' of the master that you then customize individually. Also, when you revert a setting in an overridden display it will revert to that of the master. I also think that the master display is fully saved in the database, and for all the other displays on the same view only the overridden parts are saved, hence less storage.     

The Master Display has no associated menu and is therefore good when you need a view but do not want to unnecessarily create a menu entry (ie page) or block or other views resource. It is typically used in this fashion when embedding a view in code, or by other modules that take a view as a parameter, ie Answers, and Views Field View.