winmain里用dialogbox直接创建dialog窗口，这样做有什么缺点？

#include <windows.h>
#include "resource.h"

lresult callback wndproc（hwnd, uint, wparam, lparam) ;

int winapi winmain（hinstance hinstance, hinstance hprevinstance, pstr szcmdline, int icmdshow) {
    dialogbox（ hinstance, （ lpctstr ) idd_dialog1, null, （ dlgproc ) wndproc );

    return 0;
}
lresult callback wndproc（hwnd hdlg, uint umsg, wparam wparam, lparam lparam) {
    switch（umsg){
      case wm_initdialog:
        {
        }
        break;
      case wm_command:
        switch（loword（ wparam )) {
          case idok:
            {
                enddialog（ hdlg, 0 );
            }
            break;
        };
        break;
      case wm_close:
        enddialog（ hdlg, 0 );
        break;
    };
    return 0;
}