Some clients have big plans for their website, constantly expanding and changing, and are best served using a CMS like WordPress. Others need a presence on the web, but don’t want to worry about updates or maintenance, and the need for change is minimal. In that case, a “static” html5 site has many advantages – speed, the option to keep the site cookie-free, not needing more complex hosting accounts and a maintenance-prone database, and a greater level of security than content management systems that are often attacked by hackers. Also html5 pages are responsive (so they adapt to all common screen sizes and devices), can be spruced up with effects, images and videos.
Some examples here, representative for others.