Ok, I've got what you're trying to say, at least a part of it. When similar things were happening to me (like don't feel to do/forget to do things), I thought that I was lacking some social skills. Gradually I also discovered that I'm very different from other people in some aspects. Still the former one is also true. Lacking enough social skill may make you uncomfortable in social situations. Some things are common in social gatherings, like offering drinks etc. These are widely practiced. And there are some things that are your native traits, which you could accept as normal. So it's a kind of mixup.

You said that you forget to do things or don't consider to do things like that. Do you feel difficulties while dealing people socially? Like feeling anxious while talking to people? That could be a reason why you forget to do some common things you've mentioned that others usually do.