Because the real estate industry and its allies don't want anything interfering with their God-given rights to sell steep land to people without mentioning that road-building and construction on it may cause it to slide into the nearest valley.
And because the N.C. General Assembly won't mandate disclosure and mitigation laws, neither will individual N.C. counties, even where there is hazardous slope mapping, complete and specific down to individual parcels. Like in Watauga County.
The Asheville Citizen-Times has details on this most recent demise of common sense.
It'll take another round of hurricanes (remember 2005, when part of the White Laurel development came down that hill in Boone and several people died in Macon County?), and maybe not even then, not when there's bunches of money to be made by ignoring the obvious.