I think he was trying to stick to one release, as opposed to having several because he didn't want more accusations of milking the fans.
He could have made even more money had he put out the 97 SE then the 2004 SE, then the 2007 box set, but I just don't think he's that money grubbing is all.
It was only after many of us flat out asked to be double dipped that he released the 2004 SE. I remember whole threads of people on Star Wars forums saying: "We will gladly take what you have now and also buy the super duper set later".