I'm a developer too (well, technically DevOps and a hobby dev), and I can't think of any place where it's actually needed, where a traditional app can't do the job.
Of course, nothing is strictly needed, you could write your code in assembly. But just as we built higher abstractions on that, so too do people do so for UI code. If you haven't written much UI code, then I can see why you think it's not useful, but it doesn't mean that it's not, for those who do.
