If you get a server of your own, it will work independently, so it'll have its own Operating System and you'll be able to later install server side applications directly or script-driven sites via a hosting Control Panel. While keeping the Operating System updated isn't always considered a necessity, it can be a really important task for several reasons. A more modern OS version could have better support for specific hardware, so you may get better performance for the websites and web applications which you install. Your server shall also be more safe because updates typically include security patches that deal with small issues which may permit unauthorized individuals to access your content. Last, but not least, more recent script versions, which are also released for both improved security and for additional features, may need a later version of the Operating System in order to work effectively and with their 100 % capabilities.