My boss made an observation recently. He did RoboCup when he was in college, and he found that the success of a team was almost directly correlated with the extensiveness of their debugging tools. The teams that built instrumentation to figure out exactly what their robot was "thinking" tended to kick the ass of the teams that coded very carefully and hoped it all worked.
A major component of Java and Python's productivity improvement over C++ comes from the ability to easily get clean, readable stack traces whenever anything goes wrong. It's already a huge pain when your Java stack trace says <compiled code> instead of giving you a method and line number; anything that makes that the default will cause far more headaches in debuggability than it solves.