We can look at any industry and make our own assessments as to what are the most important aspects.Reliability, Availability and Support. Cameras are tools.
We're on a computer forum as an example. If we were to have a conversation about which laptops brand is best, you'd get at least half a dozen responses. Even in regards to your one preference for "reliability, availability, and support." How about cars? Hell, how about literally power tools? You're going to find there are people that are die hard for their brand regardless of what it is.
But also directly to your point, you'd have to show a substantive difference between the support you'd get from one company versus another. And then show that that difference is enough to warrant and override all the reasons to be on another system. In other words, you have a strong preference one way. Above cost. Above performance. Above glass quality. Above glass selection. Above ergonomics. Above feature set (meaning you'd still recommend Canon cameras even if it's not capable of doing what the buyer needs it to do). "Reliability, availability, and support."
I agree: cameras are tools. And you should pick the one that's best for your work. Which may not be limited to your views on which aspects are most important.