We have forced it, quite hamfistedly, to do anything. The organic hell-evolution of web browsers turned them into do-anything sandboxed mini-OS. It meant whatever hellish code you used to write your corporate mandated web app could now become a perfectly bloated standalone application. And the demonic language that would enable it was called Javascript. It does the backend and it does the frontend. You could consider those advantages over other devices, like toasters and those handheld electronic games from the 80s.