[jbbarth]

Not the answer you would expect but still: it can also happen on large projects where the refactoring or the paradigm change is just too costly in C. The pure, raw ability to make C faster is nice, but if it takes you months of development you don't have, it's pretty useless.

One typical example of this was a few years ago (if I'm not mistaken) in the monitoring world, when Shinken released a Nagios-compatible engine in Python, and, basically the reactions in the Nagios community was that the modifications involved in Nagios (C) were just too important to be worth it.