Because it's not really a good VM.
It's full of good ideas, but also full of cruft and years of technical debt. It doesn't have a JIT compiler, (nearly) no async IO, threading support is pretty new and not battle-tested nor documented very well.
It's full of good ideas, but also full of cruft and years of technical debt. It doesn't have a JIT compiler, (nearly) no async IO, threading support is pretty new and not battle-tested nor documented very well.