Over time, changes come that make it necessary to remove buildings....to de-construct them,either because of deterioration or maybe not being wanted in that location. How much effort and bother are required to get rid of the structure affects the cost of it's demolition and impact on the environment.
This is a factor to consider when creating a house or other type of building.
Reuse of materials is possible with certain forms of building. Lumber, steel, brick can be re-utilized often times. But others like concrete, plasters, drywall, etc. usually end up in the landfill---they are mostly single use substances. One exception being what some call urbancrete (seen above), the reuse of concrete slabs from porch or sidewalk type demolition.
How we make structures is important...at the time of creation and later on when necessary to eliminate them.