If you get a server of your own, it will run independently, so it'll have its own Operating System and you'll be able to later install server side programs directly or script-driven sites via a hosting Control Panel. Although keeping the Os updated is not always considered an absolute necessity, it can be a very important task for a number of reasons. A more modern OS version may have better support for specific hardware, so you could get better performance for the websites and web applications which you install. Your server shall also be more secure because updates usually include security patches that deal with small problems which may allow unauthorized people to access your content. Last, but not least, current script versions, which are also released for both increased security and for additional features, may require a later version of the Os in order to work correctly and with their full capabilities.