It’s not an answerable question. I mean, the immediate and apparent answer would be that poorer, less educated people were more crowded together, and in those wealthy enough to spread out, aloofness became a social grace. But the fact is, Japan is believed by some to have developed an elaborately courteous culture steeped in ritual because they are so crowded in together.
I mean, it’s like looking at someone’s personality. You can look at events in the person’s childhood and nod wisely, saying “Ah HA! That’s why s/he is the way s/he is.” But, in fact, you can find many other people who grew up with similar conditions who turned out completely to be different in personality. The factors that go into creating a personality are so numerous and so subtle (which genes are expressed in the womb and why? Did the distant nod Dad gave Timmy for a greeting one time when he was busy thinking about work scar Timmy for life?) that it is unlikely we will ever get a true science of personality development. And that’s for a single personality!
Now multiply that by millions and the diverse ancestral cultures those individuals draw upon to bring into the mix that is our contemporary society. Look at the fact that other contemporary cultures may vary hugely in their norms. There are a fair number of cultures, both contemporary and historic, where the poorest and least educated keep/kept their mouths shut, and where for a poor person to start a physical fight would be to invite severe punitive measures. There are no universals here, no conclusions you can draw about societies in general.
The closest thing I can come to a generalization is that the higher status a person is, the more self-controlled s/he is expected to be. Those who do not control themselves tend to be scorned, by history and gossip, at least - think Caligula and Nero. But the form of self-control can be aloofness, or it can be elaborate and public ritual, or it can be a high degree of friendliness (noblesse oblige), or whatever else a given society teaches its elites.
Then consider that in a nation the size of the US, some 260 million, give or take, there are a whole lot of sub-cultures, and a single individual probably occupies a different spot in the pecking order of each sub-culture in which s/he participates, because the values of each sub-culture differ. S/he may or may not adjust his/her behavior according to circumstances, and this may or may not affect status within the sub-culture. Where birth or something like beauty is the over-riding consideration, behavior probably doesn’t matter as much as it does, say, in a professional association (although it does have some impact). But in most sub-cultures, behavior is important.
Also, I agree with Dangerosa.