It has been around longer than you realize and it does help because you don't get illegal defenses called anymore. You can get away with more defensive strategy now than back then. I know a lot of good coaches don't like them in the NBA. So that's why you don't see them. Also it backfires on you against a good shooting team. I wish they just get rid of it. I think more teams just try to camp out on one side of the court (old illegal defense) and force you into help. You couldn't do that back then. Only thing they don't let happen that they did in the old days is let a defender camp out in the lane. Now you get 3 second defensive calls like the offense always did.
Zone defense came into place in the early 2000s.
Zone defenses were prohibited in the National Basketball Association prior to the 2001–2002 season. The NBA currently permits the use of zones; however, teams generally do not use them as a primary defensive strategy and no zone defense may feature an unguarded defender inside the free-throw lane (a violation of that results in a defensive three-second violation, which is a technical foul). The Dallas Mavericks are an example of an NBA team that regularly uses zone defenses; during the 2011 Playoffs, their zone defense was credited with slowing down offenses, forcing opposing players to recognize which defense they were playing.[1] Zone defenses are more common in international, college, and youth competition.
http://en.wikipedia.org/wiki/Zone_defense