... rather than making up something almost certainly worse yourself, and writing all the tools and all the libraries yourself. And then maintaining them. Every

... rather than making up something almost certainly worse yourself, and writing all the tools and all the libraries yourself. And then maintaining them. Every custom CPU needs at least basic integer arithmetic and conditional branching and so forth, and RISC-V's is at least good enough that there's no reason NOT to use it as your base, since it's there already and you don't need permission.