It's because too many bad apples ruined it for everyone else by doing stuff like dumping petroleum wastes out on the ground and letting cows schit in our drinking water...or doing stuff like you see on that Hoarders TV show where rats and pestilence breeds with wild abandon causing sickness and plague upon the population as a whole...

Another issue is water supplies, infrastucure, etc. Will there be enough water? What about sewage? Septic run-off? Power supplies? Enough schools? Roads? Storm run-off? Are the roads & bridges strong enough to handle the traffic? Are the intersections wide enough? Freeway access?
All that stuff needs to be considered before you carve up Grampa's 40 acre farm into 120+ housing units, moto-cross track, shopping mall, epically palatial whorehouse, etc.