Kids are increasingly becoming rare sight in burgeoning cities.
Ultimately, everything boils down to what purpose a city should serve. History has shown that rapid declines in childbearing—whether in ancient Rome, seventeenth-century Venice, or modern-day Tokyo—correlate with an erosion of cultural and economic vitality. The post-family city appeals only to a certain segment of the population, one that, however affluent, cannot ensure a prosperous future on its own. If cities want to nurture the next generation of urbanites and keep more of their younger adults, they will have to find a way to welcome back families, which have sustained cities for millennia and given the urban experience much of its humanity.
Needull in a haystack 
Well said! I am fortunate enough to be a retiree living alone in San Jose, but unfortunate in that I rarely see a range of people of all ages close to my home. There are some young families in my condo complex, but they move out as their children need preschool or kindergarten. The city is not child- or family-friendly. The erosion of cultural and economic vitality to which you refer contributes to the isolation of seniors like myself. I am fortunate to have family and friends nearby, but I miss the diversity of interaction that my parents enjoyed.
You have rightly captured the essence of the problem. Open spaces per capita is going down.