[demick]

Caster not only gives you added camber in whatever direction you turn like I mentioned, it is also responsible for giving stability to the steering system. When you go around a turn and let go of the steering wheel, it has a tendency to self-center. Or just going down the highway, it's why you can let go of the steering wheel and the car will continue to go straight. Both of these can be directly (although not entirely) attributed to caster.