Because you have to have and manage a Kubernetes cluster, that is not something easy. Moreover scaling is not always automatic, you don't tell Kubernetes "scale this application" and it works, if the application is a monolith. You have to write it using a microservices architecture, something much more difficult.

Also, managing a CI pipeline isn't something very easy to start with, there are entire teams in companies that only do that.

In contrast running a simple server is much more simple, you install a Linux OS (probably Ubuntu server, or Debian), install a web stack (for example Apache, PHP, Mysql or Postgres these days), copy the files of your website in the root directory (/var/www), or if you are fancy pull a git repository on the server so you can update it with a simple "git pull", if you need more websites on the same machine configure virtualhosts (or use one of the many software that have a GUI to configure virtualhosts).

The second solution is much more simple, in fact is the most used solution as far as I see. Most websites doesn't need high availability, if the website of the bike repair shop that I have 100 meters down the street goes offline for a couple of minutes or even one day because I'm doing maintenance on the server really nobody notices it.