David Brooks, in an art-reflects-life take on sitcoms, suggests that recent trends favor comedies about groups of friends rather than about families. He suggests,
"the change also reflects something deeper about the patterns of friendship in society. With people delaying marriage and childbearing into their 30s, young people now spend long periods of their lives outside of traditional families, living among diverse friendship tribes."
He even worries that these sorts of living situations suggest people are trading "flexibility and convenience for true commitment." There was a recent response in the Atlantic suggesting that we could make a similar point by looking at work-related sitcoms, that overwhelmingly out-number the friendship sitcoms Brooks mentions. Though it's important to note that lots of these work sitcoms show at least "intermittent unease" with characters who substitute work lives for family lives (think Michael from The Office).