Insurance is a game involving probabilities. Let's equate a person getting involved in a car crash or not with the two faces of a coin. If you flip a coin the chance of it showing tails is (1/2). If you were to flip 2 coins the chance of both showing tails is (1/4). The probability of all the coins showing tails decreases as the number of coins is increased.
Insurance companies work with a similar principle. The total amount that has to be paid out multiplied by the probability of it happening has to be less than the amount that is collected by the company as premium. If it is not the case, either the company would have to increase its premium or decrease the amount it pays out.
About the remark made by #7, there is legislature in the US that does not allow the genetic information of a person from being used by employers, insurance companies and the alike. So people can use genetic testing for its benefits without the fear of it being misused.