Amidst a persistent property crisis in Portugal, particularly acute in the Lisbon Metropolitan Area, thousands of residential units remain vacant. This article explores the reasons why owners choose not to place these homes on the rental market, despite high demand and rising prices. Based on empirical data from successive editions of the ALP (Lisbon Landlords Association) Barometer and framed by the literature on housing financialisation, institutional trust and property ownership cultures, the study reveals that vacancy is not merely the result of speculation or neglect. Instead, it emerges as a rational response to a complex combination of regulatory instability, legal mistrust and deeply rooted socio-cultural norms. Owners demonstrate that they act not only as economic agents, but also as guardians of family heritage, navigating uncertainty in a legal and symbolic environment that they increasingly consider hostile. The article argues that unlocking Lisbon's empty housing stock will require more than tax incentives or coercive measures. It will require rebuilding trust, legal predictability and recognition of the cultural meanings that shape real estate decisions, which is an extremely demanding task. Policy recommendations include adjustments and stabilisation of rental legislation and the design of culturally sensitive engagement strategies with small landlords.