By having an option to hide/disable a module, a site builder user can easily turn off and on individual parts of a page or fragment. Without this, the only option is to delete then re-add a module when you want it back plus the module than needs to be reconfigured (a fragment can save time today with this) but there are also times when you may want to hide a module within the fragment. The hidden parts will never render on the page, but only show up in the site builder editor.