Because of a feature that solves the problem of one off scripts being difficult the moment you need a 3rd party library?

A more Pythonic way of doing this might be __pyproject__ bit that has the tiiiiny snag of needing to execute the file to figure out its deps. I would have loved if __name__ == "pyproject" but while neat and tidy it is admittedly super confusing for beginners, has a "react hooks" style gotcha where to can't use any deps in that block, and you can't use top level imports. The comment was really the easiest way.