Quick answer: Because everyone does things differently.
I have seen this with photographers and I have seen this at the corporate level. I work for a company that builds (among many other things) software to help others build software. And what always amazes me is the variability with which each developer / team / division / corporation approaches software development. The saying goes that “there is more than one way to skin a cat” and this does not manage to capture the staggering amount of variation in the way people think and act.
So … now imagine 4 people that buy the same camera. The camera has 200 features … and each person uses a dozen of those at most. So why 200 features?
That simplistic Venn diagram shows you the overlap in the way these 4 imaginary people use their imaginary cameras. The numbers represent features that each person uses that none of the others use. For example, I never use exposure bracketing in practical photography. Ever. So that means that others will have at least a “1” in that “used by me” section of the diagram when I am on it.
So now imagine this extrapolated to the human race.
And yes, everyone on the planet has theoretical access to every camera marketed by the big manufacturers. So yes, they can justify putting 200+ features in a camera to try to appeal as broadly as possible.