The finder is a built-in web app for interacting with the file system. Its functionality is deeply integrated into the web browser and serves as a hub for all file system related functions.
Since Finder is part of the browser, it needs to feel fluid and accessible like a native app (even though under the hood, it is just a web app). This means having the Finder instantly accessible when you open it (no loading) and always up to date with the latest files and changes.
Technically: