Anyone who's lived through a massive societal upheaval, collectivisation, dictatorship etc can attest to this - your ownership of property only means anything in as much as it's protected. If the state fails, or if society's understanding of private property radically changes then your investment is only valuable if you can hold on to it.
Even in the private-property loving West the value of an individuals property can often turn out to just be the amount that the state decides to pay them when they seize it via eminent domain.
Societal contracts are just collective beliefs. When the number of people upholding a particular societal contract goes to zero it ceases to exist. Just as any other belief, it requires believers to exist. Unlike, for example, the space rock that some group of sentient organisms decided to call Mars.
If the value of _dollars_ goes to zero, the house doesn't collapse. The social consensus and enforcement mechanism that protects your right to live there probably does though
Whereas for your house, no matter what its market value would be you still have the right to live there and prevent others from doing so.