Each and every virtual or dedicated server has its own Os and operates independently from the hosting servers of other customers. Updating the OS is often ignored, but doing that might have lots of advantages for your sites. The most important reason to use the most up-to-date version is that patches are typically released to deal with security holes within the Operating System code, so if you do not install the updates, you risk individuals with malicious intentions to use these holes and to gain access to your content. OS updates are also released for improved performance of the system in general and for much better compatibility with the hardware available on the market, which could directly affect the efficiency of your websites. If the efficiency and the security of your scripts is the reason to update them, you could also find out that their most recent versions require an updated Operating System to be able to work properly, so keeping the OS up-to-date is always a good idea.