Bargs
Starting a project today, I can build a client in Javascript, hook it up to an API, and I'm done. NPM and Browserify make dependency management and builds a breeze. There's very little friction in the development workflow because the front-end build process it totally separate from the server. I make a change, save it, reload the page and I see my changes live without even running a server locally. Even PHP's deployment story isn't that simple.
It's true that the initial setup is more complicated than simply downloading jQuery and plopping it into an existing project, but if you have the option of separating your client and server code, it really simplifies things overall.
From the article:
"The American author and aphorist William Feather once wrote that being educated means “being able to differentiate between what you know and what you don’t.” As it turns out, this simple ideal is extremely hard to achieve. Although what we know is often perceptible to us, even the broad outlines of what we don’t know are all too often completely invisible. To a great degree, we fail to recognize the frequency and scope of our ignorance."