No one cooks at home with a Leatherman

Well, it depends on whether the feature imposes any costs on people who do not need the feature. For example, the cost to every Emacs user of adding a new major mode customized for some obscure programming language is negligible because all Emacs users already have to know about and adapt to whatever complexity is required to support n major modes. (I am not sure, but I suspect that approximately the same thing applies to drivers in Linux.)

Well, it is a little more complicated than that because catering to a small market tends to have lower expected revenue than catering to a market that might become very big. That is a minor reason for not catering to any and all feature requests, but I believe that the major reason is that it tends to make things more complicated for the majority.