To me that's like saying compression algorithms don't necessarily make data smaller. It's true enough, but you can still make general comparisons between approaches.

If your work has an "inner-loop" situation, then the JVM can optimize the heck out of it using statistics specific to this particular execution. That's huge.. it opens up all kinds of concrete optimizations that aren't possible with static analysis alone (precomputing call targets, knowing what to inline, etc.). I'd wager this is a major factor in cases when the JVM occasionally outperforms C.

But no, it doesn't necessarily help.