Not exactly - it's way more simple than that:

Adults in this kid's life (parents) hand them a phone as a toy/treat/distraction (usually the last one). Or maybe they have something similar at home for themselves. So, a bored kid sees adult using a phone, so kid asks adult for phone.

I used to do this way before cellphones. When at a house where there was a personal computer sitting around, I was usually very disappointed at being told "no" after asking to play games on it. But I always asked. To a little five-year-old-warp-core, that's just what those were for.

Edit: ubiquitous portable computing (modern phones) would have probably rendered me inconsolable after a while.

I had this only happen once in a doctor's waiting room. "Sorry, it's a work phone. Can't risk it." Then they went to ask someone else.

I have some rude thoughts about parents that allow their kids to do this to strangers.

I now carry toy cars in my bag and give them out to kids who seem restless in grocery stores, waiting rooms, etc. It's fun. (: