money, taxes, stress, govt overregulation, govt overcontrol.
People got a taste of freedom, better knowledge.
Even if in the past people were poor they at least had a house. Having a house in western countries today = LUXURY, imagine that a trash house in West EU is around 200k, and you need to invest 100k more.
You cannot even build your own house because you will get overwhelmed with regulations, certifications, payments, taxes, waiting and etc... all this before you even started.
So raising a child in 40 m2 for which you pay over $1000 / month while babuins in govt make new regulations every day and can crash your business overnight, is not what id want