You can call out to matplotlib (or any other python libraries installed on your system), using the python interop feature (https://github.com/tensorflow/swift/blob/master/docs/PythonI...)!
https://github.com/google/swift-jupyter#rich-output has an example with screenshots.
Another reason now that I think about it, is the number of scientific libraries that I can just "pip install" without much thought (such as scipy/opencv).