Well, not entirely true.
Originally, it was a trick Indian and Pakistani bat makers used to make the bat's look better. They would take a stunning 12 dead staright cleft, and make thin layers to apply ontop of ugly looking cleft. So, instead of selling one decent looking bat, they could sell 4 or 5 and get rid of the worst looking willow.
Laterally, lighter willow has been used rather than the lower grade willow as they realised it could create big shapes.
Done effectively the laminate bat can provide more power......however, there are many very average laminates out there that will not perform as well as a decent one piece bat.
......or so i have been told........