The JVM is full of large projects that are only relevant to non-Java languages, like the vast bulk of java.lang.invoke, the Graal/Truffle projects etc. They've seemed serious about non-Java languages for a long time now. However/unfortunately, almost all the work has gone into support for dynamically typed languages like Ruby or JavaScript. Given the relative popularities of dynamic vs FP languages that's not surprising. If FP languages that relied on TCO were far more popular it'd probably have been prioritised already.