One of the main reasons why the Industrial Revolution caused a loss of social dances in Europe was the fact that it also caused the growth of cities.
Before the Industrial Revolution, most families lived in the countryside. This meant that population density was very low, and people did not meet strangers often. Such a life meant that there were few opportunities to socialize with others. Organized events such as social dances allowed people to spend time with others. It allowed acquaintances to become friends and often gave young people the opportunity to find a partner.
As cities grew and the population became more urban, these type of organized events were less necessary. People had a lot more opportunities for entertainment, such as the theatre, the opera and later on, movies. Moreover, young people had more opportunities to meet each other in a more organic way. All of this led to the decline of social dances.