The main reason I never added a native-widget implementation to juce is actually just lack of demand! It was very rarely requested, so was never a priority.
That might just reflect the kind of crowd who use juce, but I do think that native widgets are getting less important these days, as people become more and more accustomed to website UIs where every site has its own style.
Also, back when I started all this, semi-transparent HWND child windows weren't possible on Windows 2000/XP, and early OSX versions also struggled with this. The stuff I was building at the time needed a lot of semi-transparent graphics, so the best approach was simply to render the entire GUI in software and not be limited to what the OS offers. (And for many situations that still makes sense).
That might just reflect the kind of crowd who use juce, but I do think that native widgets are getting less important these days, as people become more and more accustomed to website UIs where every site has its own style.
Also, back when I started all this, semi-transparent HWND child windows weren't possible on Windows 2000/XP, and early OSX versions also struggled with this. The stuff I was building at the time needed a lot of semi-transparent graphics, so the best approach was simply to render the entire GUI in software and not be limited to what the OS offers. (And for many situations that still makes sense).