Each virtual or dedicated hosting server has its own Os and works separately from the servers of other clients. Updating the Operating system is usually neglected, but doing that may have quite a lot of advantages for your sites. The most essential reason to use the most up-to-date version is that patches are frequently released to repair security holes in the Operating System code, so if you do not install the updates, you risk people with destructive intentions to exploit these holes and to gain access to your content. OS updates are also released for much better functionality of the system in general and for much better compatibility with the hardware on the market, which could instantly influence the efficiency of your sites. If the functionality and the security of your scripts is the reason to update them, you might also find out that their most up-to-date versions require an updated Os to be able to work effectively, therefore keeping the OS up-to-date is always a good idea.