Integration with OSes (Score 1)

Firefox 2 and Thunderbird use its own mechanism to display UI. Effect is following: it doesn't look properly anywhere and integrates well nowhere. The worst situation is on Macs and KDE. Is it just a NIH trend (http://en.wikipedia.org/wiki/Not_invented_here)? Real cross-platform applications should use OS' native widget toolkits. Firefox should use GTK+ on GNOME, QT on KDE, Cacoa on Mac OS X and Windows API on Windows. As we see, browser which renders itself is just a stupid idea. Users don't care about XUL and other stuff like that.