Content management systems make life easier for businesses by allowing them to control the content on their website without having to know anything about HTML or CSS.
When you see the process that goes into making changes to the content of a website without a CMS, it begins to make a lot more sense why we have them, and the really important role that they play.
Before there was such a thing as a CMS, businesses would have to call their webmasters, tell them the changes to make, and the webmaster would then have to make those changes directly to the code. In order to get under the hood of a website you needed to open a text editor, do a lot of messing around with HTML and CSS files and then send it up to the website to the server.
Why was this a really bad way to do things? There's two reasons. First, a webmaster having to get on the phone with the business owner, or read PDFs, or emails and make these updates is a huge waste of time and opens the whole process to a lot of potential errors and it gets expensive!