I try not to think about this sort of thing because it makes me feel sad.
You are (I'm afraid) correct that many people behave like this.
I think that behaviour of the type you quote can be ascribed to people behaving like children. For example:
I am the centre of the universe and I only want to talk about ME, ME, ME!
You might want to talk about something that isn't of immediate importance to ME, but instead of listening I'll fiddle with my phone in case anybody has mentioned ME in a tweet or a Facebook post. Me, me, me!
You might be suffering but I don't want to give any time or thought to it, because it might mean that I have to think about somebody other than ME and might not be able to do exactly as I wish whenever I want.
I behaved badly towards you but I don't want to face up to the consequences of my own behaviour, so I'll just rewrite events to suit ME and avoid you.
I don't want to hear anything about ME that isn't overwhelmingly positive, ever, so dare to say anything about ME that might be construed as criticism and I'll accuse you of bullying me. Me, me, me! Slight me and I'll have my revenge.
I don't see why I should pay tax. I'm sure that I put in more than I take out. I should pay less and other people should pay more and use less. I'm not sharing my toys and sweeties.
This is why it's important to find good friends, and hang on to them! That, plus looking at examples of truly selfless people, will keep you sane.