The party was never supposed to stop, except that it has. From Jeff Thomas at internationalman.com:

The baby-boomer generation were perhaps the most privileged generation that the US has ever spawned.
Their fathers returned from World War II, eager to get married, buy a house and start a family. The economy was booming, as, during the early years of the war, the US wisely stayed out, but provided tanks, helmets and even toothbrushes to those who were directly involved in the fray.
What’s more, they didn’t accept pound notes or francs; they accepted only gold. So, at the end of the war, when the manufacturing cities of Europe had been destroyed by bombs, the male populations decimated and the governments broke, the US was on a roll. They had most of the world’s gold and had first-rate manufacturing facilities that only had to switch from making jeeps and rifles to making cars and televisions.
That wave of wealth allowed the young married couples to spoil their children with whatever they wanted.
The boomer generation reached their teens in the 1960s, and having grown accustomed to receiving whatever they wanted in life, they were young adults and wanted to party. The phrase, “sex, drugs and rock ‘n’ roll” was coined and it was an apt one. Young Americans opted for plenty of all three.