There used to be a lot of disdain on HN against people who were "just partying". While the geeks stayed home, learned for school or job yadda yadda. People who socialize were always maligned here, their socializing was supposed reason why they earned less money.

And that attitude is one part of the answer. Second is that home entertainment became easier and more fun, so people stay home watching movies, browsing internet, what have you instead of going out. And overtime, dance places became emptier and organizers demotivated.