More "liberal" countries have real societal problems that cannot be solved because "individual rights" stands in its way.
What societal beacons of moral rectitude were you having in mind?
Considering Asia's history with drugs (European imperialists growing drugs in their colonies and then selling them to China to destroy their population), it is completely understandable and a societally acceptable trade off.
I think after a few more generations of escalating drug use harming our societal well being, we may resort to similar measures.
Urbanization and education are the two most effective ways of getting a population to have fewer children. Singapore is a highly educated and urbanized country.
Maybe some families were saving up money for a cancer treatment? To start a new family by buying a house?