LBJ made it government policy and this is when it became widespread. Earlier it was shameful to have an out of wedlock child not a career. LBJ provided the means for this to fuel itself into the whirlwind of bastardy we have today.
The records of over 200 children molested in the process remain sealed to this day.
Another milestone was the transformation of divorce laws. Yet a third was the dissolution of churches as the principal source of social welfare. LBJ's Great Society was a symptom as much as a cause.