preservation of old building

People have different attitudes toward the preservation of ancient edifices. While some argue that they should be demolished to provide room for modern dwellings, I give my vote to the view that the conservation is of vital importance.
On the one hand, there are various reasons to support the immediate destruction of historical buildings. Firstly, metropolitan areas in every corner of the globe bear the brunt of population booming, thus city-dwellers struggle to encounter affordable accommodations. Paradoxically, few old buildings are suitable for residential purposes due to a lack of appropriate facilities or being in a state of decay. Secondly, so colossal is the expenditure for their maintenance and reparation that it is not worthwhile keeping them. For example, it is reported that Hanoi has to dig deep into their pocket to continue the existence of dilapidated French-styled houses built in the 19th century.
On the other hand, historical edifices are a worthy legacy and living evidence of the past, thus should be protected. Not only do they educate young generations about the nation´s glorious history but also define the uniqueness of the host premises. For example, Paris is no longer a charming capital without its a-few-century-year-old buildings characterised by pleasant geometry designs and elegant facades. Moreover, tourism has recourse to these beguiling places to attract the attention of tourists from four corners of the world, creating millions of jobs for local people. I believe that Barcelona will not able to welcome a huge amount of visitors annually without its original, captivating cathedrals and museums.
In short, I understand why people opt for destroying aging blocks but it seems to me that conservation is certainly a judicious option.