Ah I wasn't aware that the built version was published on npm. Thanks for pointing that out. I downloaded the library and ran the build process myself. NPM install pulled in about 100MB dependencies. This seemed really overkill for a 30 LOC mini library.
IMHO the majority of the web does not use stuff like Webpack / Babel (yet). Just look at all those Wordpress, Joomla installations and apps older than 2 years. So being able to pull in a frontend library via script-tag is still a must in my opinion.
Yeah, though npm is really an ecosystem built around cjs modules (though some moving towards ES6), and a lot of code now being written in ES6. In some cases, it's hard to decide to leave the ./src directory or not, in addition to ./dist for the potential of tree shaking etc.