Sidney Moncrief, Mark Eaton, Dennis Rodman, and soon Dikembe Mutombo Ben Wallace, what do they have in common?

These are players who have won the NBA "Defensive Player of the Year" award, and have not been elected, nor probably will be elected into the Basketball Hall of Fame....why does the Basketball Hall of Fame snub players who have made or make their mark exclusively on the defensive end? not to mention other defensive stalwarts such as Bobby Jones of the 76ers who was a heck of a player?