Nodemailer, a large Node.js project, has zero dependencies

This is good for Node, but would be bad for a large front-end lib.

If you're delivering code to the browser, you don't want every package to ship with its own stdlib. You want them to share dependencies.

Maybe this will matter less in the future when treeshaking is more reliable, but right now "zero dependencies" is not an unqualified advantage in the JS ecosystem.