Drivers should understand that in many states if you are pulled over by the authorities and found to be without car insurance you run the risk of having your vehicle impounded on the spot. In some states it is literally illegal for the police to allow you to continue driving once they know you do not have the proper automobile insurance. In addition to having your vehicle impounded you may also find yourself being charged heavy fees and fines by the courts. Of course, in addition to all these troubles, you may have your driver's license suspended or revoked for a certain amount of time.
Aside from the legal requirements, this is the main reason you want car insurance. If you are in an accident and you are at fault you can be held personally responsible for the costs of medical bills if a person is injured and major monetary awards if a person is killed. These costs can all but ruin most families. It can mean selling your home, selling your stocks and bonds, or selling other assets in order to pay the costs.
As you know, vehicle repairs can be very expensive. If you are shown to be at fault in an accident you may be required to pay for the repairs or the replacement of the vehicle that you hit. Again, this is money that has to come out of your pocket. As an aside to this, you are also responsible for any real property damage that you might cause. For example, if you run into a house and cause a wall to collapse, you would be required to make payment for those repairs.