There's a very good reason for that: archaeological techniques improve all the time. The idea here is to leave something for future archaeologists.
In some places in Italy, Greece, Malta, probably others I don't know, people always joke that you shouldn't try to ever do any renovations lest you end up finding something and lose your house. Some places you're almost guaranteed to find stuff if you just dig once or twice.
https://www.museofaggiano.it/en/home/
And that's just one house in one city in one country!
Edit: I strongly recommend the museum, Lecce and indeed all of Puglia!
You might be interested in The Name of the Rose by Umberto Eco, a historical novel about such a lost work.
We should only excavate what is about to be destroyed.
( And we shouldn't destroy stuff just to put up yet another shitty modern building. )
It's not a building.