ya leave the crack houses, and half burned out abandoned ones, to remove a downtown historic eyesore like the old tiger stadium.....thats my tax dollars at work.
The coloseum is in ruins for just that reason. When the Vatican was being built it was just seen as a ready source of material. It was as always happens in time no longer valued or used. So it became a ready source available "quarry" with a lot less effort. It was done in Europe back in the day just as much as its done here today.
...if it has no place in the 21st century. When I look at a lot of the pictures of decay, I see it as a goldmine of reusable material. Streets full of metal, brick, and wood. This stuff is like gold to the right people.