Congratulation to your new website. Owning a website comes with responsibilities. Like your car your website needs regular maintenance in order to stay successful. Regular updates will help your site run smoothly and not frustrate any of your visitors because it does not work properly and/or has broken links. Furthermore websites are subjects of being hacked and keeping your site up-do date will help prevent these unwelcomed intrusions.
Why are websites vulnerable? Well, your website lives in an environment that is constantly changing. Surely you are aware of the constant updates from Microsoft, Apple, Adobe, etc. Your website has to keep up with all these activities and therefore requires constant supervision.