Ahh, I see, that makes sense.
Although I did a quick search for "Software USB Host" and found this.
http://courses.cit.cornell.edu/ee476/Fi ... index.html
It looks like some students were able to make a software usb host that runs on an Atmel Mega32.
Given that the NXT uses Atmel microprocessors, and that the coprocessor is an ATMega48, I'm hopeful that a software USB host could be built for the NXT.
Of course, that's me being hopeful, anyone know if this would be possible/feasible?