I don't see how the kids "blessing" their parents with grandchildren matters much. My parents had a hard time adapting after I, as the youngest, also moved out and finally started being able to support myself, even though they had grandchildren from my eldest sibling to think about.
In the end, for them the point still stands that their own kids are adults now, and while grandchildren are fun to take care of, they aren't typically the same amount of responsibility on grandparents as on parents. It still leads to suddenly having time to think about their own life, as well as the freedom to take risks, creating the same room for a crisis.
> My parents had a hard time adapting after I, as the youngest, also moved out and finally started being able to support myself, even though they had grandchildren from my eldest sibling to think about.
"Thinking about" probably won't do them much good. Seeing them on a regular basis, on the other hand, has great effects on many grandparents. Obviously, this requires that children don't move far away from parents, but many family-oriented parents stay close.
The traditional expectation is that your kids move out to be married and bless you with grandchildren, not to abandon you to rot.