CMS is not necessarily the easiest way of putting websites online, although many people seem to think it is.
Unless your client is regularly (ie daily) going to be updating pages, and adding and removing pages, then a 'full' CMS is often overkill. It will need constant upgrades, because the developers never stop tinkering with these things; it will be at more risk of attack than a non-cms site; extensions, add-ons, or modules can stop working if the add-on dev doesn't keep up with the CMS versions; backing up and restoring is not always as easy as people pretend; and your clients will include many people who simply will NOT take the time to learn how to make even the simplest updates without constantly calling you for help. You can train them and train them, but some will never figure it out. And the thing is, in the end, many clients who believe they need a CMS never actually add or delete any pages, or even update any pages. So in many cases, a CMS is gross overkill and just adds a level of complexity that is really unhelpful, especially over time.
In contrast, you can update non-cms websites very fast, and add/remove pages fast too, if you've set the site up properly in the first place. There's no bloated software between you and the online website. Open the page in a text editor, make the change, upload the file, check it in the browser. Done.
Summary: choose the best tool for the job. And often a CMS is not the best tool.