Actually, that's part of the issue. Most of Parrot's semantics are exactly those of Perl 6 (right down to the opcodes for Boolean testing), and those don't get along well with most languages.
Rakudo on the JVM does use a JIT compiler. Surprise!
The fact that Rakudo on the JVM can take advantage of the JIT to optimize simple math in tight loops fails to impress me, but I suppose it's one more half-implemented feature you can tick off the back of the box, so hooray.