In the 1990's almost every website was a static website. In the last couple of years more and more people have been rediscovering the static website and it's benefits. Why should you consider going static?
Static websites are faster because they have to do a lot less than dynamicly generated websites. A static website just has to send the files requested. The files are already generated before you deploy your website.
A dynamic website has to gather it's data from different sources depending on the specific system used. That can mean, reading files, making database calls and calling other services. Then it has to combine all that data to one response and send that as a response. Depending on the current state of the database and other systems each reponse can be different.
Because a static website does not change you can use the added benefit of CDN's. You basicly host a lot of versions of the same website so that there's is always one close to the user, making it possible to respond really quick.
A static website has a lot less parts that can be vulnerable. Making it a lot easier to keep your website secure.
A dynamic website has all the possible vulnerabilities of a static site and adds a number of classes of possible vulnerabilities that would never be possible in a static website.
Requires less maintenance
There are just less parts to maintain. Your content, a static site generator and a webserver.
No database, no code.
A static website is just a collection of files. All you need is a webserver or specialized hosting service and maybe a CDN. Since there is no processing involved at runtime every request is handled very quickly with almost no resources.
That makes that you can serve a high volume of traffic on far less hardware than you would need for a high traffic dynamic website.
Your operations staff, or yourself, has to spend less time managing servers.
In a lot of cases your content is just files in format that's easy to edit, but also easy to version and backup. A tool the static site generator is used to generate a website from it.
For the hosting all you need is the generated website. There are no dependencies on other systems. If the files are there and the webserver runs, it works.
It just works.