I live in house that was built in the 13th century (also in Tuscany), which isn't typical, but as far as I know the building isn't of any historical significance whatsoever.
I'm no hurry to have it submerged, but I can see how various past administrations didn't think much of doing so. For a more striking example, after the second world war there was an effort to empty out the inhabitants living in precarious conditions in prehistoric dwellings in Matera (and those are almost ten thousand years old).
The submersion of (historical) buildings/villages is all about "how much they are valued?/how much does it cost to save them?" and "are we ready to spend that klnd of money?".
The latter example is a different thing, it is "health" related, just like the norms amd Laws about houses, specifying the the minimal requirements to be able to call a house "habitable", or suitable for humans to live in, that evolved during the years and nowadays are in Italy among - believe - the strictest ones, see this old post of mine that lists some of the base requirements:
Matera was an example of extraordinarily old dwellings even for Italy, not of the decision making process (sorry, that was a bit unclear).
The decision was in part health-and-safety related and in part a political issue of "people technically living in caverns makes us look bad" - the idea of fixing the living conditions in the Sassi instead of moving people in newly built houses was far from the sensibilities of the time.
I'm no hurry to have it submerged, but I can see how various past administrations didn't think much of doing so. For a more striking example, after the second world war there was an effort to empty out the inhabitants living in precarious conditions in prehistoric dwellings in Matera (and those are almost ten thousand years old).