What was the social background of 18th century society?
The society of Tom Jones's 18th century was one in which classicism, elitism, new ways of community life, and social change was taking place.
The aristocracy, particularly the nobility was held on exaggerated high esteem, and they enjoy privileges that no typical citizen could ever dream of. Those with money enjoyed VAST amounts of it, as well as land and properties. This led to the often-witnessed fact that the upper classes were idle, ill-educated, and snobbish to the core.
This, according to the Encyclopedia Brittanica:
The major European monarchies had no standard of uniform law, money, or weights and measures. Continental Europe had internal tolls that hampered the passage of goods. Britain however, had no such tolls. In the 18th century, the nobility of that country lived in the most magnificent luxury that the order had known. On the continent, the nobility were wealthy. However, the noble was, to some extent, better off than a prosperous peasant was. This is because the peasant tended to prosper with the rest.
So basically Tom, the foundling, was found by a clueless group of crass class and too much time to waste and money to spend. This is where the mockery of the story is move evident.