The entire world moved out of inline dependencies in the HTML page to a package managers. We invented bower or npm __because__ of it.
We invented bower or NPM because people thought it was a good idea to have 20MB of JavaScript on a page and 19MB of it written by third parties. Generally speaking, this turns out to have been a mistake.
For libraries or professional projects, ship your dependencies or use a build system. But for one-off projects, being able to pull in a utility library without needing any tool but the interpreter you're using or some extra build step seems like a big win.