A historic town where people still live presents problems an empty monument does not. The building being protected is also somebody's home, and those two purposes pull in different directions.
Conservation rules constrain ordinary maintenance
Protected status usually restricts materials, window types, insulation and external alterations, which raises the cost of routine repair substantially.
Residents therefore face higher expenses than in comparable modern housing, while gaining no additional space or comfort in return.
Where those costs exceed what households can carry, buildings deteriorate or are sold to owners who can afford the standard, which changes who lives there.
Short-term letting outcompetes residential use
A central property in a visited town earns considerably more as short-stay accommodation than as a long-term home, which shifts the housing stock steadily.
Each conversion removes a household and adds visitors, and the effect compounds because departing residents reduce demand for the shops and schools that keep others there.
Towns that pass a threshold find the resident population falls quickly, at which point the living part of the heritage is what has been lost.
Infrastructure was built for a different load
Narrow streets, small squares and limited water and waste systems were sized for a population that no longer matches the daily numbers passing through.
Deliveries, refuse collection and emergency access all become difficult, and these are the services residents depend on rather than visitors.
Restricting vehicle access is the common response, though it shifts the burden onto residents who then carry goods further than they once did.
Revenue rarely returns to the people affected
Visitor spending concentrates in hospitality and retail, while the costs fall on households through congestion, noise and housing prices.
Where visitor levies exist, directing them towards housing, maintenance grants and local services is what connects the revenue to the burden.
Sites that have managed this well generally did so by giving residents a formal role in decisions rather than by increasing the amount collected.
Visitor behaviour is a policy lever
Overnight guests distribute their presence across hours and neighbourhoods, while large day groups concentrate in the same streets at the same time.
Managing group size, routing and timing therefore changes the experience for residents more than reducing total numbers would.
For visitors, the practical equivalent is walking beyond the main route and using businesses that serve residents, which spreads the benefit as well as the load.