This is indeed true on a statistical basis, but as someone who is technically at the very upper limits of being a millennial I think there is a tendency to exaggerate this trend. Most of the people I grew up with live in the suburbs and have kids. It's delayed compared to older generations, but most of them have ended up there eventually. I'd also say that a huge portion of my (Seattle area) Costco's shoppers are immigrants who likely work in tech and from what I can tell they seem to be making similar choices to what older american generations have with regards to children and where they choose to live.