From the moment any construction is completed it starts to decay. While a building serves a purpose, while its utility remains valued, its upkeep is guaranteed. Later in its life it will be repaired, but there comes a time when maintenance ceases to be economically viable.
It may be tolerated until it becomes too dangerous to use and too expensive to maintain, but when a place is no longer required, when all of its possibilities have been exhausted, it will fall into disrepair and eventually be abandoned or demolished.
Supporters of local history and heritage are often heartbroken at the disregard and disrepair of older structures, but such change is part of the nature of cities and of civilisation.
Nothing lasts forever.