For me, it was just to have some fun seeing whether you can get the convenience of generics in C without blowing up the size of a "minimal standards-compliant compiler." E.g., Chibicc[1] is only a few thousand lines of code; adding Gamma to that would not blow it up by much. There's something aesthetically pleasing about knowing I can read the whole thing in a few days. Nothing like that is possible for C++ (or D?) AFAIK.

But yes --- for a real project I would absolutely recommend someone use D over this !

[1] https://github.com/rui314/chibicc