Underinsured motorist is the quiet one
Uninsured motorist gets discussed; underinsured rarely does. It responds when the at-fault driver has insurance but not enough, which on a serious injury claim is extremely common because many drivers carry their own state’s minimum. It is your own policy standing in for the shortfall, and it is inexpensive relative to what it covers.
An out-of-state driver complicates the claim
Different state, different carrier, different minimum limits, and an adjuster who is not local. Liability is still decided on the facts, but the practical process is slower. Your own collision and medical payments cover do not wait for any of that.
Unfamiliar roads produce avoidable collisions
Sudden stops for a view, hesitation at junctions and confusion at roundabouts are ordinary visitor behavior, and they put the damage on the person behind. Being a careful local driver does not remove that exposure.