Those spares are stupid. What good is it if I can't take it on the highway? What if thats where I pop my first one, and I don't want to wait 2+ hours for AAA?
You're lucky, you know that?
If one tire suddenly went, you'd expect physics to come into play, and since the other tyres are still spinning at high speed, send the car to the left, or spin if the rim hits the road.