One of the most important reasons to update WordPress is security. This is to prevent hackers from gaining access to WordPress and user websites. WordPress is always updating security and maintenance to prevent attacks from malicious code.
WordPress implemented automatic updates with the release of WordPress 2.7, originally called the WordPress Upgrader. These updates can occur while you are sleeping.
WordPress is continually making improvements to it’s software, so it is important to keep your site updated. Many fear radical updates, and the WordPress development community is determined to integrate changes to the user interface and WordPress features slowly; but they will happen, often to the benefit of the user. Over the years, major updates have brought improvements to the user interface navigation. The changes made help people move around within the back end of WordPress faster and easier. This removes any interference between your great ideas for a post and your ability to share it with the world.
WordPress.com is the testing ground for WordPress development. Many of the new features and updates in WordPress are tested on WordPress.com, thoroughly reviewing them with millions of WordPress.com users before those using the self-hosted version of WordPress get the next release. With WordPress.com as the proving ground, the core of WordPress has become much more stable, so updates occur without fear.
Some users have elected to turn off the automatic update feature in WordPress mainly because some of their old features may change or because an introduction to a new feature may occur during updates.
Change seems to scare some users. However, if you elect not to have automatic updates, you should update when you are sent a notice from WordPress. The notification from WordPress should look something like this:
To update WordPress Themes and Plugins, which can happen at any time irrespective of WordPress core or maintenance updates, you will receive a notification in the WordPress Administration Panels. Click the link there or on Appearance > Themes or Plugins > Update to update them with the one-click update feature.
The one-click update feature in WordPress is only for WordPress Themes and Plugins from the official WordPress Themes Directory and WordPress Plugin Directory. If your Theme or Plugin is from another source, check with their policy and procedure for updating.