There are still millions of people who don't have smartphones [1], for one. I'd imagine that there's a nontrivial overlap between that group and people who fly.

There are still millions of people who don't have smartphones [1], for one. I'd imagine that there's a nontrivial overlap between that group and people who fly. 1. https://www.comscore.com/Insights/Press_Releases/2014/2/comScore_Reports_December_2013_US_Smartphone_Subscriber_Market_Share https://www.comscore.com/Insights/Press_Releases/2014/2/comS...