A rookie of the year in the NBA or any other sports competition is a person that had a big impact on a team or sport - a BB-draftee might be good enough to make a difference for a Div IV or Div V-team, what would a rookie of the year look like in Div I?
It would be hilariuos to have a rookie of the year like that:
7 minutes per game, FG%25, 3P%11, FT% 36, 1.2 points, 2.0 rebounds, 0.8 assist, 2.4 turnovers...
Then if you put in some additional restrictions (amount of games, minutes per game), you would only find 1 or even 2 domestic players that would qualifiy - no fun to win a competition like that.
Awards that would make sense would be: Defensive player of the year, Scoring Champion and Most Improved player.