Ok but ... why? With that I mean, why do we need it? What can be created with PWC specifically? Is there a gallery of web games? That would at the least make understanding the use case easier.

It’s on the page: https://elenajs.com/#why-should-i-use-elena

You can create anything and everything. Web components are about extending html to make it do more, progressive web components are about rendering that on the server and progressively enhancing with interactivity in the browser. Elena solves the major pain points in doing that. Components built this way can be used in any framework.