At the core, I think there's just a lot of cultural and historical sites in Italy specifically because of the Roman Empire and its tentacles.

Then there's the fact that UNESCO sites receive funding, which Italians love.

Then Italians are (overly?) proud of their history and food and they won't pass up an opportunity to tell the world they're the best. [1]

  1: https://www.youtube.com/watch?v=Lp2uDyzxP6g