Paint Me A Cavernous Waste Shore

This morning on the train I was standing, jammed in a tiny section, crunched between people. There were plenty of people in visual range whose eyes I could catch if I wanted to. One older woman looked at me, barely any expression, and then looked away. I surveyed the rest of the passengers, and everyone seemed to carry the same lifeless expression, including myself as I caught the reflection. How did we get to this point? I began to think about each one of their lives and who they could possibly be. I tried picturing them in situations at home wherein they couldn't possibly be so lifeless. I wondered how their faces would look if they smiled. It almost made me want to yell out into the void, just one simple "HELLOooooo" to see what might happen. If there would be a response. Would it be so bad to just smile at someone? Give a friendly nod, a wave, some form of an acknowledgement that shows you are alive and not dead. Is it so hard? But therein, there's another side of the coin. Case in point:
I caught myself smiling at someone on the subway yesterday, and I think I noticeably stopped myself midway through the smile. The thought occurred to me "Why are you smiling?? You don't owe this person anything just because they were looking at you!! You're a small single female in New York City! You can't be friendly!!" You never know these days with people. Its unfortunate, but its true. So where do we find the balance?
We are all so desperate to connect with people, and have real moments, the kind that remind us that yes we are in fact STILL breathing. Yet we don't trust, we shrink into our own private bubbles where we're safe. How will we ever cease to be lonely? There has to be an answer to this...