Five point seat belts lock you to the seat not allowing you to move forward at all in an impact. If the car rolls over and the roof collapses your head and spine take the full impact. With a 3 point hopefully you have moved forward and down a bit. 5 point harnesses are used with full roll cages, which prevent the roof from collapsing. But then you need a helmet and neck restraint as you don't want your head bashing into the roll cage. I believe the roof of a car must hold 1 1/2 times the weight of the car or so. But it can still collapse in a roll over. Five point seat belts need to be
