I think there's a correlation between internet speeds/availability and loneliness. Countries with slower internet are less lonely than countries where kids/adults spend hours on social media.

Maybe the answer is in the question, one in 7 Billion is quite the fraction

To me it means that they don't have someone they can connect with. I think you can be around a group of people but if you don't connect with anyone then you will still be lonely.

I do not know how much of this "loneliness epidemic" is true, but it sure feel true to me at least.

My guess is because people are selfish, and generaly  people do not trust others.

I think that prety much sums it up mate.  Any of these two or both will prety much isolate everyone, no matter how many people are around him/her.

I don't see problems in people be alone, on the other hand, to feel alone is a big problem. There are a lot of people that like to be alone. I am not a specialist, but I think that people who feel alone are looking for happiness in other people, and this is wrong because I believe happiness is provided by yourself. Nobody can make you happy, only you. Of course you can't be happy being completely alone. But my point is that people must stop expecting a behavior predefined in their mind in other people, and start to realize who they already know.