I'm Greek and the same thing you descrie happens in Greece also. People dig to lay the foundations of their new house and find ancient ruins or artifacts. They whistle innocently and pay the engineer to cover them up and say nothing because they know that if they call the authorities it will take a decade before building work can proceed because this kind of thing is nobody's priority and the red tape is like the infinite tapes of a UTM. The total value of archaeological treasures buried under the foundations of summer houses and condos must dwarf everything displayed in museums around the world.

As to Istanbul - the City has stood there for two and a half thousand years. If you dig under the Byzantine ruins, you'll find even more ancient ruins, thousands of years of layers of ancient ruins, one on top of the other like a mille-feuille. Who's going to excavate all that? Especially when there's, you know, people living on top.

And the same goes for all the large cities that have been inhabited since antiquity all around the world. Think Cairo, Alexandria, Rome, Naples, Plovdiv, Vukovar, Belgrade, Valencia, Damascus, Baghdad, Beijing, Nanjing, Kashgar, Delhi... phew. Here's more:

https://en.wikipedia.org/wiki/List_of_oldest_continuously_in...

So it's got nothing to do with "Osmanic heritage" or nationalism. It's just not a problem that can easily be solved.