Here is the problem: You’re giving a talk, you’re trying to make eye contact with your audience, and instead you see the crowns of your “listener’s” heads pointed at you instead, their thumbs flying. Maybe they have a good reason, but be that as it may they are clearly not listening to you. When it is one or two people, of course it is easy to pass it over as urgent calls, because probably they are. When it is most of the lecture hall doing it, however, that’s another thing. It is discouraging and it is terribly distracting to have such obvious evidence of how “not riveting” your presentation is. It is not as if you can simply conclude it is a bad time for everyone, stop talking, and let them catch up with you when they have the time of day to hear what you’ve prepared, either. You are stuck giving a presentation to people who are obviously ignoring you. It is awful.
When someone takes a call or send a text in a restaurant, they’re also leaving their conversational partner ignored. No one expects intimate details of the conversation and everyone knows that the call of some people, like the call of nature, cannot always be safely ignored. With that qualification, the truth is that what people really want is for other people to put the devices away. If you’ve ever been the person without a device trying to sit through a meal surrounded by people fiddling with them, you know what I mean.
The thing is, we train the other people in our lives to expect their text and calls to be returned right this minute, even over our lunch hour. There is rarely a reason to create that expectation, IMHO that expectation is half of the problem. Again: When you’re on-call as the consulting physician for an ambulance service or if you’re a priest who might have to rush off and give last rites or even if you have children or anyone else for whom you are the emergency contact, that is one thing. Most of the time, though, let us face it, these mid-meal “urgent” calls could either have waited or could have been avoided with some advance planning. It is polite to do that advance planning, that’s all we’re saying.