In addition to other answers, physically based rendering pragmatically means that renders have the potential to be a correct simulation of photography up to a certain point. For many many years rendering for film didn't even use ray tracing at all. Lights were a single point in space with no area and shadows were done with shadow maps. Now most film rendering has shifted to using area lights, ray traced visibility to different points on the light, and shaders that (mostly) preserve energy (they can't reflect more light than what is incoming). Even game engines like Unreal 4 take these into consideration and make very crafty and pragmatic tradeoffs to maintain speed and the principles that give an increase in realism.