There's a difference between having multiple implementations, even high quality ones, and caring about it. Python is all about the reference implementation, as much as I wish that people cared about pypy and the JS community has always been openly hostile to SpiderMonkey compatibility and only cares about V8 in my experience. And Java is all about different forks of the same jdk, even if several actually independent different ones used to exist.
I will admit to not being familiar enough with Ruby to say anything about that