It definitely starts in childhood, a fascination with the big noisy mechanical thing that brings you so many new experiences, and later, fond memories of geography and family, grounding you in place and time. My childhood/early adulthood home town, long since moved away from, only truly felt alien decades later, once the last bus I saw delivered new was finally retired. My home town is now a corporate blob, with none of the charm of NBC, albeit the increasing decreptitude of financial and policy uncertainty, has a familiar feel.
I was lucky, with plenty of things to occupy my curious mind due to exposure to LT, NBC, SBG, PTE and municipal operation, and then the morbid fascination of the chaos of privatisation, through home life and family visits, plus childhood and student travel/living (London). I had and have no direct connection to buses beyond youth/school and London transport needs. Fascination with routes and networks comes easily from that basic use I guess, but it was definitely something about my neural makeup that made me notice feetnumbers, the gateway drug to all the knowledge to be found in the history and marketing and operation of buses. My dad was an engineer and tank/truck driver, so that explains the interest in the vehicle and engineering side. My degree is manufacturing, which explains why I am even interested in things like Wokington and Chiswick Works. It is with a profound sense of sadness therefore, that my lingering hopes to be a bus driver or restorer, are stymied by me knowing very well that I'd be rubbish at both.
I have maybe twenty books, and my childhood ticket/leaflet/map collection. The large piles of Buses mags were long ago thinned to a core of cherished meaning for the usual reasons, and yet even that will likely go soon, for lack of enduring value to me in middle age. I still check it for free at the Supermarket library, shamelessly cover to cover, the cost (even as a digital download) far exceeding my desire for the knowledge. I was never a huge photographer, and that only came in adulthood, once you could conduct that hobby without the shame of a visit to Boots. Being verbally abused by a driver is not fun, but it only happened once, the lack of any inherent desire to catalogue, publish or trade my photos better explains photography losing its interest for me. A collection of 1:72 scale models begun in middle age has definitely superseded all these as my collecting/visual muse, but the ticket collection will always be precious to me.
I never got too obsessive about any one specific part of the whole field (I only collected the tickets I bought, for example, never travelling simply to buy one, much less buying them second hand), never going as far as joining societies or taking newsletters. I've always been a generalist, interested in everything, perhaps suffering for that given I have always seemed to feel both quite at home and very out of place at enthusiast events. There was never really a coming out to friends and family, more of a general but unavoidable growing awareness, and I do proudly display my models. But I sense they, while confused, don't see my hobby as all that odd, given I can quite easily explain why it appeals, in a very rational way. Everyone has their thing, and this is mine, but it's not like I don't also like football and beer, like the Muggles, for whom buses seem to be magical and mysterious, and thus sadly typically avoided if they can help it. I am always amused and oddly chuffed at being seen as a Savant for knowing what we all consider to be the very basics of the bus industry.
I have never understood YouTubing or rivet counting, much less spotting (as distinct from recognition) and only briefly tried to create comprehensive fleet histories on spreadsheets. But I would be lying if I said I hadn't experimented to see if any of that sort of thing appealed, and bear no judgement on those who have these interests. Nor those who have done much deeper dives into very specific areas, or those for whom buses are far more interesting than football or beer. My hat is very much tipped to anyone who goes as far as preservation or voluntering/presenting. I've certainly deconstructed diagrams and pondered depot/station design, but only in my head. I'm the sort of guy whose interests cross pollinate and whose attention wanders if a task gets too onerous or unassailable without huge effort or commitment.
Historically, and now well in rear view mirror, some things I have done were in hindsight clearly not for healthy reasons, such as seeking knowledge/understanding or having fun. Perhaps related, I did spend hours tracing London maps as a student, and years cataloguing other people's photos (but not my own!?), which is pretty sad I guess, but I'm comfortable with it being part of who I am now, at least the former, while the latter still does seem like a tremendous waste of time. Driving ten hours in one day to attend my home town's centenary rally is both manifestly absurd and totally understandable to my sense of self. Werdly, that trip aside, I've done way more obsessive/costly/embarassing/social things in pursuit of an interest in trains and railways, but for whatever reason, perhaps the personal connection, I feel way more comfortable calling myself a bus enthusiast, and I at least know that the trains stuff was squarely about liking trains and having fun.