Imagine the following hypothetical situations:
HYPOTHETICAL A: You are in your car stopped at a red light and patiently waiting for the light to turn green. As you are waiting, an individual not paying attention to the road violently crashes into the rear of your vehicle. The impact leaves you suffering from severe injuries with damages in excess of $250,000, but the individual that hit you does not have car insurance.
HYPOTHETICAL B: The same facts as Hypothetical A, except the individual that crashes into the rear of your vehicle has the state minimum policy of $15,000 of liability insurance.
In Hypothetical A, without having uninsured motorist coverage on your own car insurance, your only option for recovery is to take legal action against the individual that hit you personally. If that individual does not have any assets, then there is no possibility of recovery.
In Hypothetical B, without having underinsured motorist coverage on your own car insurance, your only source of recovery is the state minimum $15,000 policy of the individual that hit you. You cannot get any more money.
Under Pennsylvania law, a car insurance policy cannot be sold unless uninsured and underinsured coverages are offered to the consumer, but having uninsured and underinsured is not mandatory. Consumers have the right to reject that coverage which in turn reduces the policy premium. This is why many people opt to reject the coverage. Insurance companies must comply with certain requirements for the rejection to be valid, but that is a discussion for another day.
It is important to determine if your insurance policy has these coverages and if so, how much you have. Otherwise, if you or an insured on your policy are unfortunately caught in one of the situations above, there will not be a way to be properly compensated for your injuries.