Waymo, Uber Driverless Projects Make Scanning Sensors Cheaper

"After 2020, lidars will probably be significantly smaller -- the size of a credit card or a postage stamp, according to the report."

This seems unusual to me. I presume that it costs something to make LIDARs smaller. Unlike with consumer electronics, though, there's almost no need to make them smaller. Assuming autonomous cars are the primary use of LIDAR in the future, why invest into making them smaller than they already are?