Youth unemployment rate is at a low point in basicly the entire Western world. So most are obviously not sitting at home.

To start a business or a family you need money and some stability in life. With no wage growth and high housing costs with generally high house prices, combined with high intresst rates, buying a home is incredibly hard for young people and much harder then a few decades ago. However that means more people are forced to rent, which drives up rents. This leads to a tight financial situationa nd living with your parents is a good way to save some money, to get into a somewhat decent place at some point.

The big difference is that the old generaation mainly the middle class actually benefited from the system a few decades ago, so they want it back, as it was better for them back then. So they are conservative. Young people see the current system as broken and want change. As the best educated generation ever, which is much more likely to work then their parents.