Every virtual or dedicated server has its own Os and works separately from the servers of other clients. Updating the OS is usually neglected, but doing that may have quite a lot of advantages for your internet sites. The most important reason to use the most up-to-date version is that patches are typically released to repair security holes in the Operating System code, so if you do not install the updates, you risk individuals with destructive intentions to exploit these holes and to access your content. Operating system updates are also released for much better performance of the system overall and for better compatibility with the hardware available on the market, which could immediately affect the efficiency of your websites. If the efficiency and the security of your scripts is the reason to update them, you may also find out that their newest versions require an updated Operating System so as to function effectively, so keeping the OS up-to-date is always recommended.