Alan Greenblatt

The desire to communicate privately is one reason people have largely abandoned talking on the phone as a social medium. What was once a major indoor sport, taking up hours of many people's days, is now not only more limited but may be going the way of mailed letters and express telegrams.

"Now, calling on a phone is almost like a violation," says Scott Campbell, a professor of telecommunications at the University of Michigan. "It's very greedy for your social presence, and texting is not."

Hiding from Mom is one reason texting took off in the first place, says Danah Boyd, the author of It's Complicated: The Social Lives of Networked Teens. Stretching the phone cord down the hall was no longer good enough to get away from hovering "helicopter" parents.

Boomers are still more apt to pick up the phone in professional contexts, but at work as well as home a ringing phone has come to be seen as an unwanted intrusion. "I used to think the millennials were wrong about this, but it is an imposition to call someone and say put aside whatever you were doing and give me 30 minutes of your time," says Neil Howe, president of LifeCourse Associates, which consults with corporations about generational attitudes and behaviors, while mobile phone use is up, according to the Federal Communications Commission.

The onslaught of information and time spent with screens is another reason why people are talking less, says Campbell, the Michigan professor. We keep up with family and friends via Facebook, Instagram and other social media channels. Those we're closer with, we might interact with almost constantly through group texts on WhatsApp or Kik. For many people, there's no need to pick up the phone to catch up. Your friends already know what you did last night.