The need for a content management system arises when there are instances, when you as a website owner, want to be in charge of the contents of your website. You should be at liberty in adding, editing, or removing content on your website. But, this also means you do not want to be bogged down by the hassle of knowing how to code.
This is where Content Management Systems or CMS based websites come into play. These websites gives you the convenience of having a website, and also gives you the freedom of having a command over the content hosted on the website. You could manage content in a breeze.