I have a kid who tends to eat inedible things, violently assault grownups, wander into traffic, etc, so I get pretty uncomfortable if she's at school or elsewise not with me and I don't have my phone on me and charged. If she is with me then I like to have it in case I get hurt or need help, but I often keep it turned off.
If I had no kid I might not have a cellphone. I'm not sure.