For me, it has nothing to do with social anxiety, disrespect, etc. It's all about how I value my time differently from others. In my world, there's no such thing as recreation or relaxation, beyond the occasional Halo game. I do everything with objectives in mind. I constantly have several thoughts and ideas floating around in my head that I have to coalesce into coherence, because one of those ideas might be worth further investigation.
When someone texts me, messages me, emails me, etc., that's a relatively small interruption but can easily throw everything off in my head when I'm in the middle of a thread of thought. It's even worse if I am trying to focus on a specific task at hand. Yeah, I'm a serious person, but I enjoy the way my mind works and have been much happier by embracing it instead of treating it as a sickness (like the public school system).
So when I get those handful of messages coming at me every day, I ignore most of them and reply later, if ever.
I know this hurts people sometimes, and I try to help them understand. Buy I've given up explaining this over and over again. My ideas and questions around writing a line encoder are more important than your cat photos or going out for lunch, or favors for things one can easily take care of on their own.
It's not that I don't love my friends and family, but I can't have their drivel constantly loop around in my head.