public class MyOneClassUiApp {

    private constructUi() {
        // Some Ui related Code
    }

    public static void main(String[] args) {
        SwingUtilities.invokeLater(new Runnable() {
            public void run() {
                new MyOneClassUiApp().constructUi();
            }
        });
    }
}

但是根据Threads and Swing article,从主线程构建UI是安全的：

A few methods are thread-safe: In the Swing API documentation,
thread-safe methods are marked with this text:

This method is thread safe,although most Swing methods are not.

An application’s GUI can often be constructed and shown in the main
thread: The following typical code is safe,as long as no components
(Swing or otherwise) have been realized:

public class MyApplication {
public static void main(String[] args) {
   JFrame f = new JFrame("Labels");
   // Add components to 
   // the frame here... 
   f.pack(); 
   f.show(); 
   // Don't do any more GUI work here... 
   } 
}

那么,是否有一个真正的(线程安全)的原因,通过SwingUtilities#invokeLater主要构建UI,或者这只是一个习惯,记得在其他情况下做吗？