npm i
npx parcel bundle bundle.js

This loads up tailwindcss/tailwind.css that comes with its npm package with the content of,

@tailwind base;

@tailwind components;

@tailwind utilities;

but this ends up having dist/bundle.css without parsing those directives.

Instead, by using a locally saved ./tailwind.css file with the exact same content and specifiying that instead in bundle.js, it gets parsed and produces a proper dist/bundle.css.