WordPress is the single most widely used web development platform in the world. As such, it is an inviting target for hackers, crackers, and other malcontents. To protect your investment, you must be able to maintain project security and mitigate vulnerabilities as they are discovered. Installation of updates is one of the most critical paths for maintaining site security.
Another critical reason to keep WordPress updated is compatibility. As the platform advances, your plugins, site customization, and even certain critical server components will have a harder and harder time talking to each other as intended. To maintain proper interoperability and compatibility, you must ensure all software that contributes to the operation of your project is properly updated.