Culloden is perhaps a special case in that so many who fell or were subsequently butchered are buried on the site on the orders of the victorious army. This makes it not only a battlefield but also a war grave and, as such, has a special significance and reason to remain untouched. The normal practice of those days was for the dead and wounded to be taken away by their kinfolk and they would have been buried elsewhere which leaves such battlefields as interesting historical sites but little more. Whether they should be allowed to become building sites or anything else is debateable but just consider the battlefields of World War I where so many died and are still buried there, undiscovered, but where agriculture, road building and other development goes on.