The passage below is lifted from the website www.bettertogether.org:
What does "social capital" mean? The central premise of social capital is that social networks have value. Social capital refers to the collective value of all "social networks" [who people know] and the inclinations that arise from these networks to do things for each other ["norms of reciprocity"].
How does social capital work? The term social capital emphasizes not just warm and cuddly feelings, but a wide variety of quite specific benefits that flow from the trust, reciprocity, information, and cooperation associated with social networks. Social capital creates value for the people who are connected and - at least sometimes - for bystanders as well.
I'll give more examples of this value as time goes on but if you want any single go-to authority on the subject, I'd recommend Robert Putnam, who authored both Bowling Alone (which describes the effects of lost social capital in American society) and Better Together (which describes real-life examples of how communities have benefitted from renewed social capital.
Being on active duty means constantly being uprooted from whatever community you're in (hence my desire to eventually switch over to become a Civil Affairs Officer, i.e. 'nation-builder' in the Massachusetts Army National Guard -- they can deploy me but never make me move). And constantly moving means always being a stranger.
The dictionary defines stranger in a very neutral-sounding way: a person with whom one has had no personal acquaintance. However, anyone who has ever been to elementary school knows that this word is far from neutral -- strangers are something you are taught to fear (and possibly for good reason!) In popular American culture, everyone from the Doors' Jim Morrison to whoever wrote the 'Cheers' theme song knew that being a stranger is never ideal.
For some people, however, anonymity may be totally okay -- they value their privacy above interpersonal relationships, they may already have their 'community' in their own immediate family, or they can always find instant 'community' wherever they are via a distinct ethnic identity.
I am not one of those people. I don't know if it comes from being a complete extrovert, from a lifelong intense interest in interpersonal behavior, from what David Brooks calls 'the need for recognition' or maybe just the comfort of knowing there's someone I actually could call if I were broken down by the side of the road at 3 a.m. Maybe it's the feeling of wanting to belong to something bigger that drove me towards the military in the first place. When I explained this to my friends Steve and Liza, they captured it as "not wanting to start from scratch every time you leave your house."
The 'whys' are interesting but they're not necessarily super-relevant or possible to uniquely identify. What I can identify, however, is how frustrating the past five years of living without any social capital or other appreciable sense of community have been.**
** The one stark exception to this has been the time spent actually deployed...but that represents only 15 total months of this period.