user3150201 asks:
Most Java applications don't look the same as C/C++ applications. Swing might have been designed on purpose to have a distinctive look. SWT for example tried to look native and doesn't completely succeed.
Why is it hard for the developers of the Java language to design a GUI system that copies exactly the look of native GUIs? What's different in native GUIs? Isn't it only a matter of designing buttons that look like native buttons? Or does it go deeper than that?