Grandparents are a massive help with raising kids, especially so when one doesn't have brothers or sisters.
...and?
I believe what is being said is that in non-Western/fully isolated nuclear families you have a lot of people and experiences you can rely on. So having a child at a younger age like your mid-20s is not that big of a deal.
I had a friend with parents who were retiring when they were in early high school. It sounded like a rather lonely childhood borne of a fifty year age gap. When they wanted to play catch with dad- well, dad was sixty and no longer spry.
This is entirely self-centered. The kids, instead, benefit immensely from having parents with experience, emotional maturity, financial stability, better work-life balance.
You might not get to meet your grand[grand]kids but this is a sacrifice parents should be willing to make to provide a good life to their kids.