Desktop/local usage, especially for non technical users or people working in environments where they can’t install docker (eg locked down corporate machine). There isn’t a great way to pass around a single executable or installer for a Python app. There’s pyinstaller, but it’s finicky and doesn’t quite work cross platform (you have to build the executable on the target OS).
On the other hand, OP’s setup makes it very easy to publish packages. So you can create a tarball and have a user pip install that, then run your app with a simple CLI. Or publish to pypi if you want it public. The downside is you assume the user has the right version of Python and knows how to switch versions if need be and all the weirdness that comes with that. But for web apps, packaging your app also makes it easy to wrap in a simple dockerfile that basically just installs the package and then runs it.