I think people don’t want to be alone, they usually are in the car and they don’t know what to do with themselves. Time to make a call.
Of course not everyone that’s on the phone falls in the category, and I can’t listen to people’s conversations in their car, but stand next to someone in the grocery store who’s on the phone and get a feel for the importance of the conversation.
“Yeah, yeah, I’m at the store… buying shampoo… yeah. Funkdaddy’s a douche… yeah… uh huh… I never liked him… What are you doing this weekend? Uh huh… alright, call me later.”
That’s usually the gist of it. I look at it like this, if someone else was in the car, would they be on the phone? If not, it’s probably not important.