Point Clouds are often very big. But a lot of points are unnecessary. Let's take a football field. This is in fact a rectangular flat plane. The only points you need are the four corner points. In a point cloud there could be 1000 of points in this rectangle. They could all be cleaned up.
Even a vertical or a angled plane could be cleaned up this way. As specialy pont clouds for large infrastructural area's can be a hazzard. By cleaning up the unnecesssary plane points sizes of these large point clouds could be a 1/100 t 1/1000 th of the original size without any loss of precision.