During the great Plagues of the Middle Ages, so many people died, that labor on the lord's estates became harder and harder to find.

Suddenly, the surviving peasants realized that they were in demand. They could ask for more money and even have a choice of who they worked for and where they got to work. And they found their pay more lucrative, too.

A lot of historical sociologists point to this time as the decline of the feudal system and the empowering of the common man. Almost overnight, there was a new stratum of social order - the middle class. Skilled, mobile workers who demanded a price - and got it. A radical shift in the power structure.

Now, the upper class realizes the value in keeping birth rates high - more labor and cheaper labor.
That's why they never object too loudly about illegal immigration - cheap labor is coming to them.

It's an attempt to bring back the good old days of serfdom and servitude.