I agree with you in the general case, but many people are going to be using Tailwind as part of a build step, and many of those people will be using Vite to do that build. Two options down is the option to install the CLI, which does not require any other build tools.

As for why it requires npm: I dislike the Node ecosystem as much as the next guy, but it’s a tool used for web development. Where else are you gonna install it from?