付けて害はないが、2021年現在意味のないオプションである。2017年のnpm@5からデフォルトの挙動になったため。

 Additionally, you can control where and how they get saved with some

 npm will --save by default now. Additionally, package-lock.json will be automatically created unless an npm-shrinkwrap.json exists.

nishio

>`npm install` saves any specified packages into `dependencies` by default.

> Additionally, you can control where and how they get saved with some

> * `--no-save`: Prevents saving to `dependencies`.

https://docs.npmjs.com/cli/v6/commands/npm-install

> npm will --save by default now. Additionally, package-lock.json will be automatically created unless an npm-shrinkwrap.json exists.

https://blog.npmjs.org/post/161081169345/v500