Although the climate of cocooning leads most folks to stay inside all day, a decent number still go for a walk around the neighborhood. Whether they acknowledge and greet one another, though, seems to have less to do with being sociable vs. cocooning and more with whether they came of age in an accommodating vs. status-striving climate.
Some of the folks who say "Hi" you can tell are introverts and are simply making their best effort to fulfill the duties of neighborliness, while some who don't acknowledge the other pedestrians give off socially normal rather than spergy vibes. They're just too self-important to acknowledge unknown members of the community.
The strongest demographic predictor of who will initiate a simple "Hi" to strangers, or return the gesture if it's made to them, is generation.
If someone from the Silent Gen is walking around the neighborhood, there's a very good chance they'll act neighborly. Boomers too, especially the older ones. There's an abrupt shift with Gen X, though, who are about 50/50 or less likely to say "Hi" or even exchange a nod and eye contact. And some of those who have acted neighborly may have been very late Boomers who I mistakenly took to be early X-ers. The later-born the X-er, the less neighborly they are. And of course the Millennial adults are guaranteed to either stare straight ahead or down at the ground (or phone) when they pass someone.
I remember my Greatest Gen grandparents and others their age greeting others around the community, so put them in the neighborly group as well.
Silents and Boomers (and Greatest Gen) have always been more automatic to greet people in church or other civic places, whether they already knew the person or were welcoming a newcomer. Gen X and especially the Millennials have to be prodded by the leadership to meet-and-greet.
In fact, Silents and Boomers are more likely to acknowledge and start talking to strangers from the community no matter what the setting is. "What wonderful weather we're having today," said to a stranger at the supermarket parking lot. "My, that's a lovely sweater," said to the person standing in front of them in line at the drug store. And so on and so forth.
The earlier generations imprinted socially during a climate of accommodation rather than status-striving, roughly the Great Compression of 1920-1980. Back then, the norm in public spaces was to humble yourself by acknowledging and getting along with others. You see that even during the cocooning period within the Great Compression, like Mayberry or the world of Father Knows Best, where despite being more introverted they still stopped to say "Hi" to neighbors, ask how their day is going, etc.
This imprinting effect does not get over-written even if they later become more self-centered strivers, like the Me Generation of Silents and Boomers. Striving in their case is an acquired language, not their native tongue.
Gen X and Millennials, who went through adolescence and young adulthood during the '80s and after, imprinted on an environment marked by rising competitiveness and one-upsmanship. You lower your status by having to acknowledge others. For the striver, if others are to be acknowledged, it must come off as deigning to do so — a form of social largesse rather than social duty. In any case, it comes down to individual choice rather than obligation to others.
Mirroring the Me Generation, even those X-ers and Millennials who are acting to reverse the hyper-competitive climate still struggle instinctively when it comes to neighborliness in their own everyday lives.
We may not be able to undo the imprinting of our formative years, but we do have to be aware of it and make a conscious effort to behave more neighborly to our neighbors.
PS: These generational differences cannot be blamed on changes in the racial make-up of the environment that the earlier vs. later groups have imprinted on. Certainly growing up in a minority-white environment is more likely for X-ers and Millennials, and is more corrosive of neighborliness than a mostly-white environment. But you see these generational differences in all-white communities too, where racial changes are not a factor.