Great point and many of the responses are very interesting too.
I wonder whether part of this is a habitualization of intolerance for just being with oneself - to be ok with feeling bored, for instance. Most suggestions are about "doing". Just being with oneself without a doing is painful for many from what I've seen.
I think it's what that intolerance leads to which is a big part of the problem. It's natural that we don't like being bored, but these days we have infinite means to keep boredom away that don't involve connecting with others. Why go through the risks and awkwardness of opening yourself up to others when you have a device of infinite rabbit holes and time sinks in your pocket at all times? 40 years ago it was very possible to run out of entertainment, which is quite different today.