REPLs are for toying around and learning. The Go playground provides an alternative that seems to satisfy these needs for most people. If people really missed a Go REPL then the existing ones would not be "curiosities".
People use REPLs for more than "toying around and learning." They can be very useful both for exploratory programming (which is different from toying around in that you're actually trying to accomplish something) and debugging. It seems more likely to me that Go doesn't have a good REPL because Go just isn't very amenable to general-purpose REPLs, which is the same reason C REPLs tend to be more trouble than they're worth.
> People use REPLs for more than "toying around and learning."
In all those years of Scheme, Ruby, Python, Haskell, Scala I have never used REPLs for anything other than tutorials or trying out something quickly.
> that Go doesn't have a good REPL
What makes you think that the Go REPL is not a good REPL? Have you actually tried it? Probably not, because you do not care as much about REPLs as you think do.
REPLs are for interactive development, where you try out your code live on a command line, insert working snippets into an editor, and gradually build up a working program.
Really shines when the language / REPL has decent introspection, is able to break out into the REPL prompt in the middle of your code with in-scope identifier lookups, and you're dealing with lots of libraries that you don't necessarily have encyclopedic knowledge of, yet need to get the job done under time pressure.
At least that's how I use REPLs, most usually, pry in Ruby.
