Due to the rapid expansion of global populations, many heritage sites are destroyed to facilitate the construction of modern infrastructure. In my opinion these cultural sites must be protected for their beauty, significance and potential to attract tourists.
When important historical landmarks are destroyed, the opportunity for the nation to share its traditions with the world is lost. Additionally, the tendency of previous communities to relatively over-engineer important buildings and spend a significant amount of time on these projects translates in the innate beauty of these sites. For instance, the Taj Mahal in Delhi is the pinnacle of Mughal architecture in India, and has annually attracted millions of people from all over the world to view this masterpiece, and adds to the charm of the city. Further, the amount of social impact these locations have to the local population must not be underestimated. From my travels in Sri Lanka, and given that the monasteries play a significant role in local lifestyle, the city of Kandy was built around the Kandy tooth temple, to enrich the religious experience within a modern setting.
Conversely, introducing contemporary infrastructure could provide an opportunity for economic growth. Making way for more roads and buildings could allow for more better connectivity, and a more efficient use of the existing space. For example, Indonesian forests are making way for more profitable palm oil plantations, that offer employment and sustainability to the surrounding population. This also exemplifies the possibility to make a space more productive in order to support a community.
In summary, the preservation of cultural sites is better for tourism through attraction, and the significance to the residents, while modernization allows for a more productive and efficient use of the area.