Why Not Have All Cars Equipped With a Breathalyzer?

Ontario's relatively new drunk driving polices that moved the bar from a blood alcohol limit of 0.08 to 0.05 had me thinking recently. Why not have every car equipped with a Breathalzyer? You could either have it so the driver can blow and make the decision whether to drive or not have the car start. Either way, someone blows 0.06, they can talk a walk maybe stop at Timmies and come back. If you're way over, a cab gets called.