Surprisingly user interfaces are still being developed relatively common based upon a more traditional way. It is not uncommon to see deployments in which an application is designed to have the full server to server communication based upon REST APIs and the user interface is developed in a way that an application server is connecting to the backend REST APIs and will generate the user interface to be presented to the end user.
The model of using an application server-side rendering of HTML based upon data in the backend systems is a model which has been adopted form the model in which the application server would connect to backend databases primarily. When having a backend based upon APIs rather than direct database connectivity there is no direct need to have this old model in place.
As the above diagram shows, the traditional way is collecting data from the database and have the application server render HTML content which contains both the look and feel as well as the data in one. The below images outlines the more API and micro services driven architecture.
In effect, serving your Oracle JET code from an Oracle Linux Docker base image with NGINX provides you with a small webserver footprint that can be scaled upwards and downwards when needed.