As with all things in life, there needs to be balance. They have an amount of social anxiety, but it's been getting better over the last year, as myself and other friends in our group have been taking an interest in them.
Sometimes you need to press the issue a little. It's not socially acceptable to do what they're doing. If they went to public school they might've learned better by now. If you don't gently motivate a child to grow, they never will.
Life is lived and learned by stretching your boundaries and expanding your horizons. Even if that means tasting a vegetable you don't like, every so often. Or turning off your device, and talking to someone for 20 minutes every few days or weeks.
Everyone is so eager to let others do their own thing, so afraid to ever imply that what someone chooses to do with their time might not be the best for them, especially when it's children that need guidance and training in life.. that nobody tells anybody to do anything they don't want to anymore. To a fault.
I ain't that old. I was just brought up to be kind and have manners, and that includes allowing yourself to be inconvenienced for a few minutes for the sake of someone else's interests. Occasionally and within reason of course.
Phone calls, I get that. Sometimes I send people to voicemail if I don't have the bandwidth at the moment. But that's another area where the younger generations are... Drifting away from societal norms.
It's like the college recruiter that has to keep special notes, because so many kids answer the phone in silence, they don't say hello, and so you don't know they've actually answered. Even though they scheduled the call and were expecting it. Just odd stuff.
Again, I'm sure there'll be papers written on this stuff eventually. In the meantime, it's fairly frustrating.