Each virtual or dedicated hosting server has its own Os and operates independently from the hosting servers of other clients. Updating the OS is usually neglected, but doing that may have quite a lot of advantages for your websites. The most important reason to use the most up-to-date version is that patches are typically released to deal with security holes inside the Os code, so if you don't install the updates, you risk individuals with destructive intentions to use these holes and to get access to your content. OS updates are also released for improved performance of the system overall and for much better compatibility with the hardware available on the market, which could instantly impact the performance of your sites. If the efficiency and the security of your scripts is the reason to update them, you might also find out that their newest versions require an updated Os in order to operate effectively, consequently keeping the OS up-to-date is always a good idea.