What do they both do best? Money-transfers! Money quote:
While almost 2% of U.S. grandparents live with their grandkids and provide full-time care, the most common type of grandparental support these days is just plain money, a resource that travels across vast distances and is (nearly) impervious to cognitive decline ... While it might not be the same as helping to gather food or help a new mother with domestic tasks, it may just be the modern-day equivalent for the generally well off. Education level is highly correlated with socioeconomic status, which in turn is related to overall health and longevity, so perhaps putting the grandbaby through Harvard is sort of like bringing home a basket of wild veggies every day for 18 years.