First of all you can't make the assumption that just because someone owns a lot of land somewhere that they can build on it. The towns in which Patterson and Walkhill is in may have limited their expansion efforts. They still need to get permits and zoning rules in order to build.
Also just think about this. In Brooklyn with building stretched out over a number of blocks, can you imagine the transportation department needed in order to occupy Brooklyn. Just to move laundry from residences to the laundry required trucks and personnel to transport it.