Quote Originally Posted by A.P. Photography
And why is that, please explain.
lots of reasons I guess...

Red-eye reduction beam from lamp compared to strobe from actual speedlight on Rebel XT. Beam is easier for subjects to distinguish from actual flash firing. (Less eye blinking effect).Compatibility with older lenses including manual focus Nikkor lenses (AI-P and D type), and non-CPU.Higher resolution LCD playback monitor with 130,000 pixels compared to 115,000 on Rebel XT.Exposure compensation +/- 5 EV compared to +/- 2 EV.