The 3 point shot goes both ways for teams that concentrate on it - you live by it (when they are going in) or you die by it (when they aren't going in).
If there was no 3 point shot, then short guys wouldn't really have as much of a chance. The worse shot in basketball right now is the long 2 pointer.
The 3 point shot also opens up the inside play (stretches the defense). A good team will play the outside and the inside. Hitting the 3's makes a team defend the perimeter while opening up the inside for the big man play or the dribble drive.
Some evolve with the game as it evolves and some don't.