I saw a cartoon by Piero Tonin that to me was too real to life for me to laugh. The cartoon shows a boss with a phone in his hand talking to his employee. The boss is saying, "Would you mind if I made a few calls while I carefully listen to your ideas?"
This is more reality than it is a joke. I see this message delivered non-verbally, multiple times each day. It isn't always as blatant as the cartoon (although at least the boss is asking permission) but distracted conversations are a common occurrence
For example, I was recently meeting with an executive and reviewing a detailed and complex proposal. As we were visiting, his smart phone continually beeped as he would receive an incoming text message or email. EVERY TIME that the phone beeped, he would immediately turn on his phone and read the message - sometimes even while he was attempting to share his thoughts at the same time. A few times he even had to ask me to repeat my last comment because he had missed what I was saying as he read his message. Soon, I pushed back my chair and completely disengaged from the meeting. If our time together isn't important enough to shut off the phone, turn off email and/or focus, then why should I waste my breath and best thinking? He is free to waste his time since it is on his dime. I get paid the same either way.
I see this happening at the dinner table (not just with teenagers), in restaurants, in meetings, on conference calls, in social settings, during training events, while driving, etc. People think that they can mentally do two things at once or carry on two conversations at once. But the reality is they are distracted, not completely processing ideas and wasting the other person's time - not to mention that it is extremely rude and offensive.
If you are consistently carrying on distracted conversations, you should consider what type of message you are sending. You should also realize that trying to do two things at once means that you are actually not doing either thing well at all.