Because emacs in most implementations is not project aware the same way an IDE is (like the ways eclipse preprocesses the project and holds a coherent data model in memory while you edit) it just doesn't have the tools available to even build off of. It was only post-LLVM that tools for that kind of formatting and editing are expected to be coming from the compiler's AST itself (things such as https://langserver.org/ is pretty exciting). I think Go has some of the best source code at command line tools, but they are leveraging that there is a 'one true way' of go tools to work that is easy enough to deal with so a simple command can do just enough work to do what needs to be done as opposed to a C/C++ application that is a #define soup with custom build infrastructure that emacs has no way of getting a coherent model out of to decide whether it can refactor things or not.
I keep trying to make emacs work for it, but it turns into a lot of custom tooling that I really don't have time to build for the kinds of applications I end up having to work with. Emacs is still superior for actually reading and writing large bodies of code, just it is awful on operating on the code at a syntax-aware level and doing the same quality of IDE-grade checks to make it a mechanical thing as opposed to a brain-driven thing.