Simple saying "unnecessary" is or "driveways to not improve navigation or add clarity" not a legitimate and enough reason of why such objects should not be mapped on osm. 

Driveway mapping is a vaild and legitimate type of object as it can see from areial imagerys, even on grounds levels which can be seen publicly from the roads or streets, meet the pricinple of "on the ground", which stand as important principle of OSM.