Duke has never had any pull as a program within the University. This limits the number of guys who can get in, because if you want to go to Duke, you basically have to get yourself into the school and then have the privilege of joining the program. This is the dance that all the programs have to do at the top top academic schools, and is what makes Cornell's and Princeton's (relative) success so impressive. They bring the school a considerable amount of positive clout, so I imagine they have a bit more pull come admissions time.
Duke doesn't have that. The coaches can't just tap a guy on the head and say "I deem him worthy" and get him in.