That example is of course invalid because buying a truck doesn't involve massive amounts of other parts that only work with a Chevy.
Buying a Chevy locks you into a dealer network. It locks you into where you can service your vehicle. I decided not to buy a particular brand because the service center was too far. You're also buying into that brand's repair costs.
Let's face it, buying a Nikon isn't like buying "Brand X." It's a known quantity with lots of followers. I would have to say that for the majority of people, and I tell this to nearly everyone asking me camera buying advice, the brand is of little difference. For some
people with very particular needs, it makes sense. For me it makes huge sense. To someone who does serious landscape work, 36MP + dynamic range that kills the 5D3, it makes perfect sense.
If you are a wedding/event photographer, it makes no sense at all. None. Switching brands is idiocy. Likewise, if you don't make a living from your gear, it doesn't make a lot of sense to switch. I still contend that blind allegiance to a brand is irrational and that an informed buyer makes decisions based upon the full breadth of information available and a careful analysis of needs and what meets those needs.