A big part of the reason was that I had no idea anything was unusual until a few years ago.
If you grow up with one way of viewing something, and it never occurs to you or anyone else to share experiences of it because it’s so basic, how can you realize things are different for others?
When considering social struggle, I assumed I had difficulty only because of surface problems like clothing sense or basic appearance or voice: things that were possibly amenable to training or improvement.
It was only after the discovery of the possibility of face blindness that my counselor and I were able to work backwards and consider what effect it might have had on my early social relations. I always hung back because I was trying to figure out who people were before saying Hi. This was especially important if I needed to figure out whether any of them were going to attack me (I was bullied a lot ion senior public school). It may be that this gave other people an impression that I was aloof and unfriendly, or not interested in people. Did this lessen my chances in the social world? I suspect so.
A few months of frequent contact will give me an array of things to check off when figuring out who someone is, but rapid recognition is never trustworthy. As I mentioned before in the case of the woman in the blue sweater, combine a new context, new clothing, an unfamiliar hairstyle (I’d seen it before once), and insufficient time, and recognition fails. It doesn’t matter how long I’ve known anyone.
The general effect is something like being surrounded by an eternal costume ball. Everyone’s identity is obscured by a mask of varying opacity, and only the people I’ve known well have tramsparent masks that I can see through and see who they are. But that developer at work I met twice is a masked figure saying hi in the hall. And if the light reflects oddly off the mask of someone I’ve know for twenty years, I can’t see them either.