When housing markets are extremely tight, people fear improvements. Improvements mean the neighborhood will be more desirable. More desirable neighborhood means

When housing markets are extremely tight, people fear improvements. Improvements mean the neighborhood will be more desirable. More desirable neighborhood means people with more money will be interested. More people with money means higher rents. In tight housing markets, people come to see the unlivability of their neighborhood as a shield to defect attention of people who could price them out.