Most millennials were born in the 1980s, smart phones didn't come about until 2006+
Most of our lives were outside as kids. I got my first cell phone at 18, 2 years after I had already been working 40 hour weeks while going to school and my parents finally got sick of not having a way to get a hold of me. Comically their cell phone bill went down because the company I worked for gave them 25% of their bill when they added my phone so they didn't want me to have a separate plan.
I still remember my mother calling me sometime that year and asking if I'd come to dinner and I had to tell her I was over 1,000 miles away because I flew to Boston.
I think I was 22 when I started staying indoors more. Took a desk job and got overweight and lazy.