Not sure about now with multicore, but pretty sure OCaml had a "bump" memory allocator previously. These are just a little bit slower than stack allocation as they just involve a pointer increment and is important in functional languages since they allocate a LOT. Go's memory allocator is pretty fast (I played with making a bump allocator for it and it was only 4-5x faster, so very fast), but the slowdown would be noticeable. Also, Go uses a "mark and sweep" style collector (which is the reason it can't use a bump allocator - those require moving on collection, which Go can't do) which just isn't designed for the amount of garbage that FP languages generate. It might work, but it would be quite a bit slower.
Go uses a simple non-generational collector because it avoids generating garbage on the heap by doing escape analysis and allocating on stack. I get the ocaml does a lot of recursion, being functional. But could stack allocation also work for ocaml when using growable stacks?
People forget that the call stack data structure naturally allows tail calls, and restrictions against it invariably have a certain degree of artificiality.