Because buildings change constantly.. notice how in the examples, you have building for which this requirement must not be fullfilled. Public show-off buildings

Because buildings change constantly.. notice how in the examples, you have building for which this requirement must not be fullfilled. Public show-off buildings, statues, temples and harbour walls, they do not change with every generation. Now if you want to change it constantly, if a building is for living, durability is actually not that much of a value.