I am not certain there is only one culprit but one could be technology which doesn't help our sense of belonging. We have never been more connected yet never as isolated as we are today for there is no substitute for one to one human contact and social media tricks the mind that one is getting it.
There are also more single people out there than ever. The combination of the young unmarried and the older divorced or widowed is creating a legion of the lonely who may not be getting the adequate amount of human contact.
Loneliness is a high risk factor for mortality (in fact one of the highest) which is why some countries are focusing resources to try and combat it for it strikes at the heart of the stability of a society. The fabric of the way we live is changing rapidly but we are not improving the quality which may just be the victim of speed and efficiency at all costs.
We may need to roll back the speed at which we live just enough to get a glimpse of all those disconnected souls.