Why aren't there LiDAR records in some black and white parts of the scene?

This is the actual scene:

This is the corresponding LiDAR scene:

The LiDAR data is from xyz file. The questions are:

• Why are there no points for the dark squares on the checkerboard as well as the wall behind? Similarly, why are there no points for the floor but points for the “holes”?

• Are xyz files preprocessed so that the undesired points are “removed”?

_{I’m new to LIDAR and point cloud processing so I’m seeking for help here.}