Why programming competition contestants use C++ and Java?

The answer really comes down to what I think is a very under-discussed issue in development: Proficiency with the tools you know can in many cases be better than switching to the "right tool".

You see all this talk about choosing the right tool for the job, which then gets twisted to mean everyone needs to have exposure to 20 different languages such that you can make the "best" decision. When in many cases, whatever tools you're the most proficient with is the "right tool" (for you).