Do archaeologists or other relevant experts have any sense of how common these things were / what fraction have been destroyed either through natural processes

Do archaeologists or other relevant experts have any sense of how common these things were / what fraction have been destroyed either through natural processes or human activity? Are there a smallish number of these sites because they were always rare (and took a lot of labor to build) or were there a lot more of these but like a lot of them were deconstructed by iron age farmers or something?