How users are getting benefitted by hiding the hidden windows from Mission Control?

Some important features (such as showing all windows including the hidden ones) of Expose is not available in Mission Control which replaced the former in the recent versions of OS X.

If this decision of Apple is not an accidental mistake (I think so because this is happening through 2 or 3 successive versions of OS X), how users are getting benefitted by hiding the hidden windows from Mission Control? (Why Mission Control should not show all windows, by assigning appropriate styles to the hidden and minimised ones?)