Each and every virtual or dedicated server has its own Os and works independently from the servers of other customers. Updating the OS is usually ignored, but doing that might have a wide range of advantages for your websites. The most important reason to use the newest version is that patches are frequently released to deal with security holes inside the Operating System code, so if you don't install the updates, you risk people with harmful intentions to exploit these holes and to gain access to your content. Operating system updates are also released for improved performance of the system overall and for far better compatibility with the hardware available on the market, which could immediately impact the efficiency of your websites. If the functionality and the security of your scripts is the reason to update them, you could also find out that their newest versions require an updated Os so as to operate properly, so keeping the OS up-to-date is always a wise idea.