For us, we care about all that stuff, because we are engrossed in it daily. For everyone else, they will never touch or understand and / or should never need to understand what a kernel, filesystem, sound system, or desktop environment is. To them, the computer is a tool, not an environment, and to use it is to press buttons to get some tangible result you want from it, and the buttons you have are not buttons you are going to know how to change.
So I want a choice in kernel, filesystem, etc because I care about the semantics, performance, ethics, and implementation of these things because I interact with, code for, and code against, them on a near daily basis. Everyone else does not know they exist, and thus don't care, so choice is irrelevant to them, in the same way the existence of Linux as an OS "choice" does not matter to them - if it is not on the notebook on the shelf at Best Buy, it might as well not exist.