The bike business isn't a career choice. It's something you get sucked into and trapped in.
Small shops have traditionally been owned and operated by bike enthusiasts who wanted to share what they liked. This is, apparently, a terrible business model if you want to be profitable. The ragtag survivors of the industry press have produced thoughtful articles about how we should all be more businesslike.
As true as that may be, the far reaches of the bicycling universe are still served by small shops staffed by poor idiots who didn't know when to give up and move on. We've stuffed our heads with things no one needs to know.
In the 1990s, our shop's advertising tag line was, "we really ride!" The mountain bike boom had brought a lot of weak players to what looked like a feast of easy money. The happy salesman chatting you up in a big shop might very well have to go find a caustic grouch in the repair shop just to put air in his tires. While some top racers were notoriously mechanically inept, you do much better as a rider if you know something about the machinery, and much better as a problem solver with the equipment if you really ride.
Experience comes with time. It's vital in a repair shop, where the equipment coming in could be weeks or decades old. You can learn a lot from books and videos, but they're not as good as personally witnessing the evolution.
Imagine being a veterinarian and the animals are evolving visibly, drastically, from year to year. The old ones aren't dead yet, but the newer ones have extra eyeballs, or six legs, or you have a dog with gills...
It takes more than intelligence, and lots more than theoretical engineering to keep the nation's bike fleet operating. Newer isn't automatically better. I know, I beat the crap out of that concept relentlessly, but I do it because it is true. It is the most important truth about bikes. Old stuff -- not ridiculously old, but not fresh from the mold -- can keep going for years, and serve you well. You just have to know how it works. And that's where you need that witness to evolution.
My colleague in the repair shop is a fully grown retired engineer. He missed the runaway evolution of bicycles in the 1990s. He's constantly getting ambushed by weird problems with old componentry that can be nearly impossible to diagnose if you didn't go through the maze with it when the industry first inflicted it on the riding public. Some of it never worked and never will, but most of it can be coaxed to function far longer than the manufacturer ever wanted it to.
Just as the dead vastly outnumber the living, so do the old bikes vastly outnumber the new ones. The continued popularity of fixed-gears indicates how the old ways can persist and be built into new machines. If you know where to look, you can find friction shifters. You can assemble your own cassettes, for ultra-personalized gearing, as long as you are willing to forego brifters, and relinquish forever the idea of a manufacturer's technical support. We don't need no stinkin' tech support!
People pay huge money for a 300-year-old violin because the qualities that make that human-powered musical instrument great have been worked out for a long, long time. Machinery like a bicycle cannot age as gracefully as a fine violin, but the qualities that make a well-fitted bicycle the perfect machine to convert human effort into forward motion have been worked out for a long, long time...relatively speaking.
Well below the Stradivarius level, your basic bicycle can provide decades of use with proper care. Perfect for a courtesan or a priest to ride after supper.