According to some statistics, WP powers a fifth of the Internet. It means that there are resources for everything. There's excellent community support and a plethora of plugins and customization options.
Drupal can be customized to do almost anything. It was built ground up with the intent of using a wide variety of small modules to get the exact result wanted instead of just the most common solutions.
Drupal is not easy to get into and out of the box doesn't offer much. To get Drupal doing what you want it to, modules are required. To get modules, an understanding of how Drupal works is required. And that takes time.
Admin interface is constantly being iterated on to remove unnecessary legacy features and to streamline the interface. Resulting in a very clean and easy to understand interface that also offers a wide range of options.