One point that seems to be ignored in this discussion is that having a GC creates problems for interfacing with foreign libraries. It's not too hard to create h

One point that seems to be ignored in this discussion is that having a GC creates problems for interfacing with foreign libraries. It's not too hard to create hooks in the runtime to allow calling C functions, but it's very hard to go the other way, and usually you have to write bridge code in C that links to both the language runtime and the foreign library. And no matter what there will be function call overhead that's unacceptable in some circumstances. Languages runtimes enable lots of other cool things, like JIT compilation and runtime specialization, user-space schedulers and I'm sure some other things as well, but if, as a language designer, all you want is GC, consider if that's worth all the costs of having a runtime.