Bright people, especially bright young people, often do not understand this.
Generally, I agree with most of what you wrote, but just on this point, I'm not so sure. Some of it is due to changing culture, perhaps, and, possibly, even how engineering is taught. You need social, collaborative events at college/uni for (say) introverts to get to know how to deal with others, and team events, even quizzes, sports, where there will be failures, but also empathy, etc., so people learn how to literally shake hands afterward and conduct post-mortems without embarrassment.
It's deeper than just 'thanks'. Getting things wrong and knowing how to deal with it is important. For instance, it's OK not to know something. But on forums (and sadly perhaps even in some firms), it can often be either ridiculed, or you're "minus-one'd", or people will misread and perceive they are being ridiculed because the culture in engineering and sciences or some vocations or some firms might be to expect to be the subject of such derision if you "mess up".
Self-inferiority, traumatic events, or stresses can lead one to think more inwardly and less considerate about others too. All manner of subtle things in life could cause it and perhaps get worse as people are supposed to mature.
Even if youngsters have not been brought up right, or if it doesn't come naturally to some, it can still be learned. There's a good book by the well-known Debrett's. Some of it is anachronistic, but it doesn't hurt to learn a bit of that at the same time. It also gives one a little confidence in many social circumstances throughout life, including work-related ones. I quite like the classic "I'm OK, You're OK" too. Sure that too is ancient, but there's still something to learn there. I'm sure some would even ridicule wanting to self-improve through reading these sorts of books. But better to leave a good impression than a bad one if you can in any interaction (not always possible; if you recognize someone is deliberately being argumentative and looking for a forum-fight (easy to spot sometimes; for instance, those who will call anything "woke" to see who will respond to that, or YouTube videos that start with a false premise and a question-mark), it may well be better to terminate the discussion; the more emotionally intelligent you are, the easier to do this; in some cases, it may wind up the other person more, but better that than escalate further and leave distaste for everyone to read through).