The fact that most people enjoy exactly the opposite of what I do was revolutionary to me, really explained a lot, and allowed me to navigate social interactions better.
Having said this, I don't see the ROI on pleasing people I don't like. I try to gauge whether someone has the same vibe as I do, and if that's not the case, then I'll be polite but that's it.
Second, less common but still common mismatch: different emotional responses. If an event happens and I react in way A while the other person reacts in way B, either of us needs to suppress the emotional reaction, which is exhausting. I'm not willing to do that, unless genuineness is not expected by definition (at work, at family reunion).
The catchup, as mundane and obvious as it is, at least signals to the person that you see some value in them and value your relationship, even if it's transactional in nature. Does it need to go on for paragraphs or multiple emails back and forth? Absolutely not, but having some lead in makes it less like you're only concerned about what you can get from the person.
Would you rather a waiter just come up to your table and say "Order!?" or have a little bit of pleasantries before asking what you'd like to eat. There's no more transactional relationship than a diner and a waiter, but most people would prefer the latter.
Some people have a very hard time adapting or accepting different cultural expectations, and their world is necessarily narrowed. It always makes sense logically, "Why should I have to play these games to show that I mean well, people should judge me by my more meaningful actions" but another way of looking at it is it's not worth it to them to make the microscopic effort to communicate willingness. If they're not willing to make even that little effort to make communication easier, what else are they unwilling to do?
Psychopathy is not about choosing not to feel empathy - it's a neurodevelopmental disorder characterized by persistent deficits in emotional responsiveness and empathic concern for others (meaning they can't). -"opathy" is usually a disorder outside of one's control.
This is why I said psychopathy "can be" the selective inhibition of empathy, because by some definitions that's what it is. Other definitions like yours essentially define it as what I call sociopathy (simply being without empathy in the first place). I don't claim my definition to be the only definition because psychopathy can sort of mean either thing depending on who you ask, but I use my definition just for the sake of argument.
They want to be appreciated, acknowledged, and seen above almost everything else. If you call up an old acquaintance and start the conversation by asking if they know of any job openings, you will be seen as someone who only values what they can DO for you, instead of who are they ARE to you. Nobody likes being a tool, they like being a friend, and like feeling that they are doing something good for someone that likes them for who they are.
Now, we ALL know that the call out of the blue to catch up often has an ulterior motive but it's polite (and necessary) to at least PRETEND that the ask is not the main reason you called.
But if you called, and you are not even slightly interested in catching up, that just makes you a rude ass.
We're social animals, and when people overtly signal that they're disinterested in the existing paradigm, they're communicating that they're going to be exhausting to interact with, since you're going to have to explain and justify every individual thing you want out of them that they don't already understand, and they'll never just go along with things for the sake of others.
This I feel is unfortunately counter to the design of humankind, where we are—as you said—social animals and the only way to change for the better—at a species level—is to change together.
I'm talking about "open handed" issues where people tend to debate and negotiate: preferences, not convictions—if 3/4 friends want to go get a sandwich, but 1/4 insists on either salad or "go without me", this can be taxing on the relationship—especially if they also are usually open to sandwiches and have no strong conviction against it.
It's not that people who clean up after camping have to drag all of humanity with them before they can claim to have done some good - it's that the sandwich shop example doesn't have anything to do with actual human values.
This might out me as a psycopath, however, cut to the f'ing chase. If it is a transactional conversation don't insult my intelligence by pretending that it isn't. Obvioulsy this can create a problem as I tend towards "Do unto others as you would have them do unto you".
If something is within my means and the person hasn't made it onto my shit list I love to help out, it's what makes getting up in the morning worth while. Unfortunately we are all far more powerless than anyone can imagine and actually being able to do more than point people in the right direction, offer advice or just talk to someone is incredibly rare.