I would guess one reason it wasn't done in other languages was because people simply didn't have a good cross-architecture JIT compilation resource, and didn't want to write it themselves. LLVM makes this _really_ easy. I realize that Zig is transitioning to an LLVM-optional model now. But, for instance, I've been working on an s-expr language with f-expr application, and this combined with LLVM c bindings allows you to generate arbitrary compile time or runtime code. The JIT portion for compile time code was a single function call in LLVM! I started this a while before Zig came out, but alas I haven't devoted enough time to it over the years...