I do not think it is a new trend, so much as a growing trend. When I was in school, you didn’t really have that. Furthermore, a single parent not by the death of one of them was uncommon too. The gutting of the nuclear family, and it relative unimportance to many, as well as shifting marriage to a mere commodity, left many children in the hands of a single parent, unfortunately usually the mother. Who had no real resources to care for the child or because of ideology that keeps her regulated as a child instead of the biological young lady she is, her income opportunities are lessened even further. Then when you regulate sex to a mere commodity and you had all the fixings for this grandparents raise the kids brew.
Sure back some time ago, many generations live under one roof or in the same area, but cars, jet travel etc. made it easy to scatter to the four winds of the nation, or the world, for that matter. Those days are pretty much dead as the nuclear family is headed, or females marrying when they were late teens and early 20s. Today it is more about, ”getting mine”, and enjoying one’s self, and if part of that enjoyment produces a child, suck it out, or pawn it off on the grandparents, they always said they wanted one anyhow, usually.