First, Web technologies (not just JS but HTML, CSS, DOM, etc) are implemented by multiple browsers, who compete and have other agendas, as well as backend and n

First, Web technologies (not just JS but HTML, CSS, DOM, etc) are implemented by multiple browsers, who compete and have other agendas, as well as backend and non-Web platforms. This underlying technologies are just messy in a way that only a world-wide, massively distributed, twenty-year-old platform can be. There's nothing quite like this anywhere else in tech, as most platforms are dominated by a single vendor. Imagine what Windows development would be like if, in addition to the need for backwards compatibility, there were three or four competing vendors of Windows, each with different feature sets and bugs. Second, tools and libraries can overcome many of these problems, but these fixes come with costs, including library maintenance, cognitive overhead, security risks, complex build and deployment processes, and retraining and hiring issues. Because JavaScript is used across many industries and teams of all sizes, what is perfect for one may be completely inappropriate for another. Many projects, like GWT, meet the needs of the environments in which they were designed, while being so much a product of those environments that they become anti-productive elsewhere. So we have a very diverse set of tools on top of a very messy and relatively old set of underlying technologies. Finally, many new programmers come into this incredibly diverse, sometimes frustrating, environment every year. It is an environment that encourages open-source contribution. It's no surprise that many new tools and libraries are released every year, and some of them gain adoption.