It's very true ham radio has a very rich almost unique culture.
I obtained my license many years ago whilst I was still at school and I've developed many friendships with those within the Amateur community, and despite me not having been on air for many years, many of those friendships forged in the days when I frequented the airwaves have endured to this day. In fact many have turned out to be more rock-solid and stable than just about every other friendship I've had.
I'm not alone, when questioned many amateur radio operators will express exactly the same view.
Why this is so is perhaps up for debate, but I'd put it down to a number of reasons: Amateur Radio is unique amongst hobbies in that it operates in a very different way to most other hobbies perhaps the most significant of which is that it requires a government-issued license before one can operate on air—and to obtain that one has to demonstrate both technical and operational proficiency in radiocommunications by way of passing examination. There's no shortcut or other way around to obtain an Amateur license, as passing the examination is a mandatory requirement.
Of itself, that requirement alone binds amateurs together. Thus not everyone can become a member of this unique club, as it's only through the involved procedure of passing the Amateur examination that one is able to be initiated into the Amateur fraternity.
One's solidarity with the the Amateur movement becomes even more solid after one learns the rules, procedures and etiquette of Amateur Radio culture. In a sense once one becomes an Amateur one then becomes indoctrinated into this long and esteemed culture that owes many of its origins to government-necessitated rules and procedures—rules that have still deeper origins in that they derive from ITU—International Telecommunications Union regulations.
Having to conform to ITU regulations is perceived by Amateurs more as an necessity rather than an imposition, as by the time one becomes an amateur radio operator, one knows that he or she—along with others—has the privileged responsibility of ensuring that the electromagnetic spectrum is properly managed. Not only is that responsibly not seen an imposition by Amateurs but rather it's seen by them as a necessity, as proper management of the spectrum is vital for all radiocommunications services to operate in an optimal way. Mismanagement of the spectrum would result in interference between services and from external sources, radio regulations and procedures ensure that interference is kept to a minimum.
Being part of the worldwide fraternity that sees itself as having such an important responsibly—a responsibility that doesn't flow from being paid but out of the love of it and of one's hobby—further strengthens bonds between Amateurs.
Even though I've not operated on air for many years I still consider myself to be a member of this tightknit community. Once an Amateur radio operator it's forever.