Who's to assume that the person the car is registered to was the person driving it at the time? Don't let anyone else ever drive your car!
Former PennDOT employee here. The following comments are true in PA. I would guess that most other states are probably similar; some may be wildly different.
In PA the registered owner of a vehicle is responsible for the use of that vehicle, no matter who they allow to drive it. It is incumbent upon the registered owner to only allow individuals they believe to be of sound judgment and character to operate their vehicle.
Of course, that excludes most of my family on my wife's side. (insert rim shot here)
So yes, the registered owner is at least partly on the hook for whatever happens with their vehicle when someone else drives it. The owner must be very judicious in who they allow to drive their vehicle.
This is also why, in the event of auto theft, the registered owner must report the vehicle stolen as soon as possible.