Each virtual or dedicated server has its own Os and works independently from the servers of other customers. Updating the OS is usually neglected, but doing that could have lots of advantages for your sites. The most significant reason to employ the most up-to-date version is that patches are frequently released to deal with security holes in the Os code, so if you don't install the updates, you risk people with malicious intentions to use these holes and to gain access to your content. Operating system updates are also released for improved efficiency of the system in general and for better compatibility with the hardware available on the market, which can immediately impact the functionality of your websites. If the functionality and the security of your scripts is the reason to update them, you may also find out that their most up-to-date versions require an updated Os so as to work effectively, thus keeping the Operating system up-to-date is always a wise idea.