Even if you have the immobilizer on your new car, if a potential thief thinks your car is one of the stealable ones, you may still end up with a broken window.
However, if you’re risky enough that no insurance company will touch you, but you are able to financially mitigate your risk to other drivers, many states will allow you to fulfill your legal insurance requirements by self-insuring. So it’s technically not correct (in many states) to say that you have to buy insurance. You usually just have to be able to prove you can afford the risk of a (minor to moderate) accident. For example, in California, you can deposit $35k at the DMV and drive with no insurance.