A computer to call balls & strikes - why not?

[MoreWineII]

I know the technology's there so why rely on these inconsistent strike zones that vary from umpire to umpire when some sort of laser or something could probably call balls & strikes with 100% accuracy?

The strike zone is defined in black and white. There's no "judgement" that comes into play. If the ball crosses the plate in the strike zone, it's a strike. If not, it's a ball.

Opinions?