Content Management Systems (CMS) are a way for people to use and create a website without actually having to do any of the coding, they just sign up and start adding in the content, like WordPress!
They have become very beneficial for anyone that just wants to blog, or make a small website for their business. It takes the hassle out of having to hire someone to create a website for them and having to also stay in touch with that person if they wish to change anything about it. That saying, it is also taking these jobs away from people who love to build and create websites.
Although CMS are great for getting content out there on a smaller level, they would not be very beneficial for a larger company. For larger companies, someone that is actually hired to take care of the website and coding of the site is crucial.