The reason why we have fewer friends now is because we have optimized life for economic growth, not happiness. Technology is the primary thing to blame here. If we didn't have technology, we would have to rely on each other more and we would not have social outlets like the internet to provide a superficial social bandage to our underlying social needs.
It's also the width of the economic growth mindset. We fuel the 'have more devices and be free-er and independent' so naturally people can live on their own (misery).
I may be imagining things but when you live in a small place where you have no choice but to share the load and pleasure of life (granted the group is emotionally stable), you don't suffer from that. You're a jolly bunch making your place nicer, finding and cooking food, and being goofy at night around the fire.
You know what I mean, not too crazy / violent. Of course it's never absolute peace. But at the same time this is one factor that drove 'modern societies' to more and more isolation. It's tempting to not want to deal with others. But at that point it's detrimental.
It's an interesting question but it won't stop. I think the question is (for the individual), how can you organize your life and your priorities so that friendship plays a more central role in your life?
