If you get a server of your own, it will run independently, so it'll have its own Operating System and you could later install server side programs directly or script-driven sites through a hosting Control Panel. While keeping the Os updated isn't always considered a necessity, it can be a very important task for several reasons. A more modern Operating system version might have better support for certain hardware, so you may get better performance for the sites and web applications that you install. Your server will also be more safe because updates usually include security patches which fix small problems that may allow unauthorized individuals to access your content. Last, but not least, more recent script versions, which are also released for both increased security and for additional features, may need a later version of the Operating System in order to work properly and with their full capabilities.