Why It's Okay Not to Have Many Friends and How to Appreciate It

I stumbled upon a picture of my friend's wedding on Instagram. There were people around her, people who used to be my friends too and I was not there. Oh well, I'm not inside the circle anymore, I guess. As I was observing it, I was wondering why most of my friendship didn't last long. I never had more that 7 people in my packs and most of them drifted away and move on with their lives as I move to another place. I find that I questioned myself a lot. Where is everyone? Is something wrong with me?