[mike_hearn]

That's not correct. The first UI toolkit Java had was AWT and it mapped through to native widgets. AWT was not very successful because it tried to be cross platform rather than a direct mapping of the Windows UI toolkit, which was significantly more advanced in that era than its competitors MacOS Classic and - most problematically - UNIX workstations, which had truly miserable UI toolkits. So AWT was limited to the lowest common denominator and trying to abstract UI libraries didn't work very well, the abstraction was leaky.

So for the first few years of Java's existence developers were given native UI, and said no, actually, we don't care if we have a native look and feel or not - for the kinds of line-of-business apps they were writing a powerful and consistent toolkit was more important than one that looked the right shade of grey. Hence, Swing.

Nowadays if you want to write a small, pure native Java app with native widgets you can do it with SWT and Avian. There's an example here:

  https://readytalk.github.io/avian/

It demos all the features available in SWT with a 1mb download that's fully self contained. You still have the problem of leaky abstractions and SWT apps don't look entirely normal, as some more complex widgets still need to be custom, but it's another attempt at AWT that works significantly better as MacOS and Linux closed the gap with what Windows could do, so you can have a richer abstraction.