Hype
Misdirection
Thoroughness
A lot of reasons, really. Besides, the non-Shirou-and-Kairi Masters of the Red team had very sparse "profiles." It wasn't much more than a name and a goofy title aside from Sembrem/Senbellum, and even that was a simple blurb about his being a Clock Tower instructor. The Yggs got full character designs very early on. I still remember thinking, "Gee, I can't wait for the Red side to get its own reveal, too!"
The creators were brushing the Red Masters under the rug from the very beginning, but I bought into it because I figured it was just a matter of time before we got more information. But now I realize why we never got that information. They were never meant to be important.