Many Drupal developers don't notice how many confirmation pages or small forms exist that take users to a separate page; I wanted to streamline that experience by reducing the number of page loads and redirects. And since dialogs come with Drupal core I decided to leverage that and create a custom module that would do a couple of things:

handle most of the Drupal core page dialogs
make it easy to configure for developers in their installations.
I've been using modal and off-canvas dialogs in most of my custom modules and found it to be a really nice addition. This informed what has turned into the Admin Dialogs module, which I just launched this week.