Or your question just seems so out of touch that it is easy to confuse someone as being under the influence of drugs. This is the public internet and we have no way of knowing who you are, what state you're in, what kind of health conditions or situation you have, or even what culture, age, gender or intelligence you have. We all just assume that people are of average intelligence and know how to use a computer and get online to a forum like this ... which makes us think that the person is fairly intelligent and capable (not that anyone on Lemmy or the Fediverse is automatically a genius). So it was easy to assume that someone asking the question you did was either someone without a lot of experience, someone with little education, someone under the influence of drugs or someone who is intelligent and experienced and just pretending to not know.

To get away from either making fun of someone, belittling them or even dismissing them - I'll attempt to answer your original question as openly as I can.

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Simply put, as others have pointed out, it does not make sense to cover up already excavated ruins. They have already been disturbed and for us to cover them up now would just further degrade them. We have already contaminated them with our world and if we bury them now and someone else uncovers them a thousand years from now would just confuse future archaeologists. It would be like us uncovering a ruin of something that the Romans had uncovered, disturbed and buried a thousand years ago ... all we would see is that they did something for some reason, buried it and left it ... we have no way of seeing what they did, what they found, why or what context - all of that previous knowledge of what was there is now lost, unless someone wrote about it all.