What do you think? There are many good players, some better than the ones that were picked. So with 10 total picks, why draft a lesser player or any player if you had no idea if they were even interested in playing?
Provided that USHL affiliates are eligible to be rostered on NCDC teams, it's a worthwhile gamble.
In some cases, a young USHL draftee doesn't make the team out of camp, and then has to find a place to play/develop for a year+. Prep used to be the only option, but now that kid could play NCDC for a year, or until he makes the USHL roster.
Older kids could also realize they are outgrowing Prep, and see NCDC as a better option than playing against younger kids for another year.